Front Range Food Gardener

New USDA Hardiness Zones Announced

2012-01-25T12:14:00.007-07:00

Okay, so most vegetables don't overwinter (asparagus, rhubarb, Jerusalem artichoke and a few others being the exceptions). However, vegetable gardeners are concerned about climate and length of growing season. They are also interested in flowers and herbs for attracting pollinators to the vegetable garden whose persistence may be determined by hardiness zones. Fruit growers certainly have plant hardiness concerns.

What's exciting about the new, online 2012 USDA Hardiness Zone Map announced today? It's been updated to the Internet age with cool, online features. In addition to being able to put in your zip code and automatically get your zone, you can also enter your state name and see how climate works locally.

The coolest feature though is the Interactive Map that shows the streets in your area with the hardiness zones detailed. This is a vast improvement from previous maps where you had to guess your location on an all-to-generalized map. Be sure to click right on the map and use the +/- slide bar to zoom in to your neighborhood.

That said, what has changed with this revision? First, know that plant hardiness zones detail the average annual extreme minimum temperatures at a location for a given time period. In this revision that is the 30-year period from 1976-2005. These zones don't reflect historic lows that occurred before then or might occur in the future.

Compared to the previous 1990 map, the update shows most areas are a half-zone warmer (5 degrees F). In fact two new zones have been added to the U.S., 12 and 13. Each zone is a 10 degree F band that is subdivided into a and b. Most of the Front Range is now 5b with some 6a.

Grow on! - Hairy vetch

2011-12-30T08:35:00.014-07:00

It's nice to see something green in the vegetable plots in winter and hairy vetch, Vicia villosa, performs well as a cover crop. It is is a high N producer, vigorous grower, very drought tolerant, prospers in low fertility and a wide range of soil conditions, and is winter hardy to zone 4 with snow cover.

One of the best things about fall planted hairy vetch is that it provides improvements in crop yields greater than the nitrogen added by it's symbiotic nitrogen-fixing bacteria alone. This may be due to root penetration that leads to better vegetable root development, physical soil improvement that allows a better air-moisture balance for crop roots in soil, improved soil biological activity or other reasons.

Note that hairy vetch doesn't build up long-term soil organic matter. It is a essentially a succulent plant that has a relatively low carbon to nitrogen ratio in the range of 8:1 to 15:1. Most benefits are realized by the first vegetable crop that follows in spring. For this reason it is often interplanted with winter rye, Secale cereale, that has a higher C:N ratio (ranging from 25:1 to 55:1) and thus breaks down more slowly. The combination planting results in some of the best of both worlds - N contribution plus short and longer term organic matter increase.

Hairy vetch growth is almost non-existent in mid-winter but will increase with lengthening days. Mow and turn it under at 25% bloom when N contribution will be maximized.

Note that freezing temperatures under 5 degree F can cause some winter kill if there is no snow cover. Temperatures in this range occurred along some parts of the Front Range December 5 and 6 and some damage may be seen. This is another reason to plant with hardy winter rye so an adequate spring yield of biomass can be gained. Next post will highlight workhorse winter rye as a cover crop.

Photo credit: Hairy vetch closeup - Carl Wilson

Season Endings and Beginnings

2011-10-07T13:11:00.014-06:00

Vegetable Endings
With night temperatures predicted to drop into the thirties F this coming weekend, it's time to harvest what remains of tomatoes, peppers, eggplants and many other fruiting vegetables. Thirty degree temperatures are flavor killers for tomatoes anyway so using ripe fruit and ripening mature green or pink breaker fruit indoors is preferable.

Cover Crop Beginnings
Clearing plant refuse off the growing area now has another advantage. Mid-October is a good time to plant winter cover crops for soil improvement. Maintaining desirable levels of both organic matter and nitrogen in your soil is important for growing vegetables. Nonlegume cover crops help with organic matter and legumes can add both.

One common cover crop planted in our area is winter rye but there is a lot of confusion about what that is. Winter rye is cereal rye, Secale cereale, the same rye used for grain. Annual or Italian ryegrass, Lolium multiflorum, can be used as a cover crop in certain circumstances but winterkills in cold, dry Front Range conditions. Annual rye should be sown in early fall, so it's now late to plant.

Winter rye on the other hand is one of the hardiest of cereals and can be seeded later in fall. Growth is rapid in cool fall weather and its quick-growing, fibrous roots hold soil and leftover fertilizer well. It is also good at suppressing weeds.

Rye can also be sown with legumes in fall. Hairy vetch, Vicia villosa, is one of the most popular. It's winter hardy to zone 4 and can work in zone 3 with snow cover. It grows slowly but root growth continues over winter and vine growth quickens with arrival of spring. It tolerates poor soils (including sandy ones) and delivers a heavy contribution of nitrogen compliments of it's symbiotic nitrogen fixing bacteria.

A type of field pea (Pisum sativum subsp. arvense), Austrian winter pea, can also be used as a winter legume. It is not as cold hardy as hairy vetch and should be seeded in early fall. Plant it with a winter grain such as rye to protect pea roots and maximize winter survival. It prospers best with some winter moisture.

A rule of thumb is to plan for at least a month in spring after turning under cover crops to allow them to decompose before planting vegetables.

Photo credit: Tomato harvest and Rye/Hairy vetch seed - both Carl Wilson

Other root vegetables - parsnip

2011-09-30T12:58:00.008-06:00

Parsnips are just now coming into their own with no need to worry about rushing to harvest before frost. In fact freezing actually improves root quality so bring on the cold weather. Roots can be dug as needed or stored moist (vented plastic bags) in the refigerator for a couple weeks so starches are converted to sugar for roots to have a better flavor.

Parsnips are grown from seed planted in early spring (April). 'Harris Model' and 'All American' are two standard varieties but most should grow well here. Fresh seed is a must as old seed germinates poorly. Like their parsley family cousin, carrots, seed takes 2 to 3 weeks to germinate. Seed is often over-planted because of poor germination and then seedlings thinned to 4-6 inches between plants.

This is a full season crop averaging 110 to 120 days (4 months) to mature. A deep, loose soil is a must just like carrots. Once top foliage grows to cover over, most weeds should cease being a problem. Supply steady moisture to avoid root disorders but note overwatering can cause forking and hairy roots. Moisture fluctuations produce cracking. Organic mulches (grass clippings or straw) in summer are helpful for weed and moisture control.

Parsnips are a different root vegetable to try for a variation from carrots and beets.

Photo credit: Parsnips in raised bed, harvested parsnip roots - both Carl Wilson

Seasonal roundup

2011-09-21T15:54:00.028-06:00

Powdery mildew
With cooler weather comes a decline in production of summer squash and increase in powdery mildew on both summer and winter squash. Hopefully many fruit have been harvested or are near-ready for harvest. Photo is of powdery mildew on Kabocha winter squash. Powdery mildew decreases photosynthesis and weakens plants affecting nutrients available to form fruit and their flavor.

Control is mostly preventive through a full sun location and good air circulation. Water at the soil level rather than on leaves. Potassium bicarbonate (Remedy) can be used as a preventive or in the very early stages of infection. Some fungicides such as neem (Greenlight Powdery Mildew Killer) and horticultural oil do have some effect on killing existing infections.

Cabbage aphids
They're back......! Cabbage aphids thrive in cool fall weather and can be a real problem on savoy cabbage and Brussel sprouts (photo). They penetrate in and among the curled leaves and where sprouts set down in the leaf axil. Their feeding distorts and contaminates the harvest. Cabbage aphids overwinter on wild mustard family plants so weed control near the growing area is important.

Control is tough because of their waxy covering that makes these gray-green aphids appear bluish-white. Lady beetles don't like them because of the wax. Syrphid flies are another predator that may help. Unfortunately the activity of predators decreases late in the season when short days and cool temperatures reduce the activity of natural enemies. Parasitic wasps aid the cause but parasitized aphids tend to tightly stick to foliage compounding contamination problems.

Botanicals such as azadirachtin insect growth regulator, neem oil or pyrethins can be tried as well as horticultural oils when insect population thresholds warrant applications.

Destroy crop residue after harvest to minimize overwintering populations.

Photo credit: Powdery mildew on Kabocha squash, Cabbage aphid on Brussel sprouts - both Carl Wilson

The big cool down

2011-09-08T12:05:00.011-06:00

In our semiarid climate, it's always amazing how fast the weather can cool down as the days shorten. Some folks I talked with the last week of August were despairing that it would cool down anytime soon. Then, wham. The first of September was officially 96 degrees F in Denver with a 68 degree low. By the 3rd it was 71 degrees with a 48 degree low.

The losers in the vegetable garden are the warm season vegetables. Tomato fruit have slowed ripening and summer squash are not producing fruit seemingly overnight. The winners are the cool season vegetables for those who had the space and foresight to seed them mid-summer (July).

Nights under 55 degrees F will cause tomatoes to shut down for a few days to a week, especially with nighttime temperatures reaching 41 degrees F, the official low on Sept 4th. Mature fruit on these plants will eventually ripen but the cold affects flavor. New and young fruit tend to stop development.

This is the time to think about season extension growing tunnels if you want to keep these crops producing through the fall. When temperatures drop 14 degrees below the desired 55 degree nighttime, tunnels almost have to be plastic on hoops as row cover fabric only provides a few degrees of difference.

Even though these temperatures are ten degrees below normal and we will likely still see some warm days, more nights in the forties are predicted over the next week. The cool season leafy vegetables like lettuce, spinach and kale are loving the temperature change to cool and don't need season extenders in early fall.

Photo credit: Two types of kale and lettuce - Carl Wilson

Beet leafminer

2011-09-01T16:21:00.015-06:00

Beet or spinach leafminer is generally more of a cosmetic pest on beets grown for roots. For greens, it is another story.

The leafminer is the larva of a 1/4" gray fly with black hairs. Eggs are laid on leaves or several plants including beets, spinach, chard and weeds such as lambsquarters. Small maggots emerge and tunnel between leaf surfaces. The narrow tunnels merge into pale blotches (photo) and damaged leaves are distorted. Maggots drop to the ground to pupate and change into adult flies.

Leafminer emerges in April and May and several generations occur each year. They are active now on spinach and beets planted mid-summer for fall harvest and particularly common in gardens where one or the other crop is continuously grown.

Eggs are distinctive (photo) because they are white and laid in small masses. One of the simplest means of control is to check for egg masses and hand crush. Pinch leaves to kill karvae inside when mining is observed. Leaves with actively growing larvae also can be picked and destroyed or bagged for trash to be taken off site. Leaving picked leaves on the ground allows leafminer to complete its lifecycle.

The use of floating row cover fabric can help if put in place before flies emerge and the crop is in a different garden area than the previous year. You don't want flies emerging from the soil under rowcover with their favorite food handy and protected.

Control weeds around the garden and rotate crops for control.

Photo credit: Leafminer blotches on beet leaves (Carl Wilson), Leafminer eggs (CSU Extension)

Banner year for tomatoes

2011-08-29T16:17:00.017-06:00

Although many people on the Front Range may be tired of summer heat, there is always a plus side. One is that it has been a banner summer for productive tomatoes. This is due to hot days but more so to warm nights. Many nights have been in the sixties degrees F instead of fifties as is so often the case in Front Range summers.

After a cool May and transplanting better delayed until the first week in June, some people were despairing of realizing a tomato yield due to a late start. This has obviously resolved itself and many varieties are showing good performance.

In full sun, 80 day heirloom 'Cherokee Purple' in our garden is doing as well as 73 day modern 'Big Beef'.

Three short season varieites tried this year are of note. 70 day 'Azoychka' from Russia (photo above right) is a mild acid, yellow fruited type that is producing well. A 68 day pink Asian type, 'Zhefen Short' (photo left) from China is yielding a good crop of nice plump fruit. The heirloom 75 day 'Black Cherry' (photo right) is also bearing nicely.

Shorter season types of 70 days or less including 'Early Girl' (62 days) and heirloom 'Stupice' (52 days) from Czechoslovakia (photo right) are still good bets especially if you have only part day sun or a cooler location. They bear early and can perform well in summers that don't have warm nights. Both have produced well for us this year.

Harvest from the demonstration garden at our Denver office is donated to feed the hungry. Consider donating your excess bounty to a local food pantry or soup kitchen.

Photo credit: 'Azoychka', 'Zhefen Short', 'Black Cherry', 'Stupice' tomatoes - All Carl Wilson.

Harvesting fall squash

2011-08-22T15:35:00.028-06:00

I've received several questions about when fall squash are ready for harvest. Fall or winter squash should be harvested when fully mature which is more typically in September than August. Immature fruit have a watery flesh, don't store well and if harvested are eaten like summer squash. Not all of them will taste good when eaten immature, hubbard and golden acorn reputedly are O.K.

As fall squash matures, the flesh becomes drier and sugars develop. Both changes contribute to storing quality. Some types will store up to 3 or 4 months when harvested at the right time and stored under ideal conditions (dry and 55 degrees F). One inch of neck should be left on the fruit and it should be hard and dry when harvested.

General signs of maturity are skin that can't be easily dented with a thumbnail, color that is true to mature type, and reaching the proper number of days to harvest.

Certain types of squash have other things to look for. On acorns, the groundspot where fruit touches the ground will change from yellow to orange. Carefully turn fruit over to check being careful not to detach from the stem in case you have to roll it back to let it ripen further (photo acorn above left - still yellow: immature). On golden acorns, the groundspot doesn't show like it does on green acorns. Yellow skin should turn a deep golden yellow at maturity on these.

Butternut squash are ripe when vine growth stops and skin color changes from a light whitish tan to a deep tan (photos below - left photo immature, photo right fruit medium mature and still needs time to turn a deep tan).

Vegetable spaghetti squash are mature when they turn from a light yellow to golden yellow (photos below). Buttercup squash are ripe when dark green fruit are 5 to 6 inches across and stop growth. These are the most common varieties grown by home gardeners because their approximately 80 to 85 days to harvest makes them reliable in our climate.

Blue hubbard (blue-gray) and Boston marrow (reddish-orange) are occasionally grown. They take a full season, 110 and 120 days respectively, and are mature when vines die down.

Photo credit: Rotating acorn to check maturity, Butternut immature and medium mature, Vegetable spaghetti immature and mature - All Carl Wilson

Squash viruses

2011-08-12T13:09:00.018-06:00

Several viruses affect squash including squash mosaic virus and cucumber mosaic virus. Aphids transmit the viruses from infected plants that can include weeds such as common lambsquarters, kochia and others.

You may discover viruses as we did recently in our yellow zucchini planting by spotting one plant with light green, mottled leaves in a sea of healthy. dark green leafed plants. (Click photo to enlarge). Leaves often have a mosaic pattern and may be distorted, have deep lobes, or appear string like and thin.

Fruit can appear small, deformed, mottled, have ring spots or exhibit color breaks and may develop warts. In our planting the affected fruit (photo left) look quite different than normal yellow zucchini (photo right). The different viruses produce different symptoms depending on the stage in which the plant is affected and several viruses can affect the same plant.

Do plant virus resistant or tolerant varieties when available. Purchase seed from a reputable supplier and use care in saving seed. Manage aphids to keep numbers low. As soon as diseases appears, remove plants like we did. Viruses can be mechanically transmitted so wash hands and tools before working with healthy plants. Control nearby weeds that may harbor viruses. There are no pesticides to control viruses.

Photo credit: Virus mottled leaf plant stands out, Virus distorted fruit, Normal yellow zucchini fruit - all Carl Wilson

Tomato pruning debate

2011-08-08T16:16:00.010-06:00

I've had several conversations about removing tomato suckers with people recently. Suckers for those who don't know are the shoots that grow between the tomato leaf branch and the main stem. If you choose to remove them, do so when they are young rather than letting a large shoot develop. The question is should you remove suckers or not?

There certainly are some pluses to this growing technique: easier to train on a support whether stake or cage, ability to plant more plants closer together and easier access to harvest fruit. See photo of tomato in a pot with slim form produced by having all suckers removed. The alternative is not pruning which usually is done by letting tomatoes run on the ground. With large, 3 to 4 feet wide, sturdy cages, not pruning is also often practiced.

One of the disadvantages of removing suckers is exposing fruit by having less leaf cover. This can increase the chances of sunscald (photo). Sucker removal carried to the extreme probably limits the photosynthetic capacity of the plant particularly with some less robust tomato varieties.

You also can use some of both techniques along the way. Removing suckers at first and then slacking off and letting them grow later produces more leaf cover to protect fruit from sunscald. What works for you?

Whether you are pruning or not, you should have fruit beginning to ripen. Nighttime temperatures are already beginning to drop into the fifties along the Front Range. The August transition to fall will also see more daytime temperatures in the eighties. For warm weather loving tomatoes, fruit development should be well along at this point in the growing season.

Photo credit: Tomato plant with suckers removed, Sunscald on green tomato fruit - both Carl Wilson

Seed or transplant for Fall

2011-07-26T16:08:00.018-06:00

Now is the time to finish seeding or transplanting 50 to 60 day crops to mature in Fall. We just finished installing kale, red and golden beet transplants (photos). Even though it's hot now, these crops and others including lettuce will grow and be of good quality as they mature in cooler fall temperatures.

Planting a second crop where spring crops leave "vacancies" increase yields from a given square footage of soil during a growing season. Rotate crops and don't plant same family plants such as kale following cabbage. We planted beets following lettuce and cabbage, and kale following beets.

This higher demand on garden soil is equivalent of a full season crop such as tomato or potato. It requires adequate organic matter and fertility to meet the needs of the second crop so do be sure your soil is prepared to handle succession planting.

Photo credit: Transplanted kale, red beet, golden beet - all Carl Wilson

Hail recovery hope

2011-07-20T20:34:00.016-06:00

To encourage those with gardens struck by hail, this post features pictures from a previous year's hailstorm. While chances of recovery depend on the extent of the damage, plants can surprise. Fruiting vegetables always seem to sustain the worst damage, particularly the big-leafed vegetables like squash and pumpkins. Roots escape underground and regrow. Leafy vegetables generally come back.

These photos of tomatoes and straightneck summer squash are from a July 21 hailstorm. White hailstones are visible in tomato photo. Click on photos to see enlarged view.

The photos below show plants August 17, about a month later. The Yellow Taxi tomato is sparse and shows hail-nicked foliage but did ripen fruit. The summer squash put on an amazing amount of growth and more fruit.

Photo credit: All five photos in post - Carl Wilson

Use of Mid-summer Transplants

2011-07-02T13:46:00.010-06:00

While many people think of transplants as only a May start-of-season planting technique, they can also be useful in midsummer for planting crops for fall harvest. In midsummer you don't even need a greenhouse to grow them!

There are always two ways to plant - direct seed or transplants. Mid-July is a rough date to have 50 to 60 day vegetables direct seeded to mature for fall. Using this target date, you can plan whether transplants or direct seeding will best work in your crop scheduling following spring crops.

Perhaps you have a crop growing that won't be harvested in the end of July and direct seeding another would not allow it to mature before frost. Answer is grow transplants. Or perhaps you have difficulties directly seeding the garden because of wind and sun, soil crusting or other physical soil condition, inability to frequently water to germinate seed, garden pests on young seedlings or whatever reason. Transplants may work better for you.

Growing transplants in pots placed on the ground (or bark mulch) as pictured works well. Floating row cover fabric thrown over the pots and tucked under the trays conserves water and helps seeds to germinate. Remove when seedlings have begun to develop true leaves or leave on to protect from birds and insects. Grow for 4 weeks or so and you are ready to gain a jump on the fall harvest season by transplanting into your growing beds.

Photo credit: Trays of pots growing on bark mulch, Kale (bottom) and beets (top) grown as midsummer transplants - both Carl Wilson

Cool to Hot update

2011-06-26T21:44:00.020-06:00

Flea beetles are a concern on tomatoes that were set out in May before weather was settled. These plants were stunted from the cold nights and have struggled to begin rapid growth even with the last week of hot weather.

Key to overcoming flea beetle feeding is to promote rapid growth of transplants and seedlings. Flea beetles jump from the soil and attack lower leaves first (photo right). If a transplant grows rapidly as did this tomato set out June 5 (see photo left), they overcome injury. For details and control suggestions for flea beetles that infest tomato family, cabbage family and other plants, see the CSU Extension fact sheet Flea Beetles.

Cilantro flowering has promoted more questions than usual this season. The quick change from cool to hot weather caused plants to rapidly develop flower stalks. Both temperature and day length influence flowering. In hot weather during the long days of summer, cilantro rapidly produces flower stalks with ferny foliage as opposed to the desireable flat leaves (photo shows both).

Plants induced to bolt produce flowers and set seed in four to six weeks from time of sowing. If you purchase transplants, they can quickly start to flower too. Grow plants in cooler shade to delay flowering. Sow a succession of cilantro seed every few weeks through the summer to produce a constant supply of the herb. In cooler spring weather, cilantro will keep in the leafy stage weeks to a month longer.

Note that if plants go to seed, you can make coriander spice from grinding the seed instead of harvesting cilantro leaves.

Photo credit: Flea beetle injury lower tomato leaves, Tomato transplant outgrowing flea beetle injury, Cilantro - All Carl Wilson

Hail NO!! - But for some unfortunately YES

2011-06-19T17:38:00.014-06:00

June is always an unsettled weather month in between cool May and hot July. Hail has already been a worry for growers and some have already taken their licks. A June 8 storm nailed Ft. Collins and a short pelting got a vegetable project I'm working on in Denver on June 13.

Vegetables with broad leaves take it hard as evidenced by the broccoli photo right. Soil may also crust afterwards as seen in this photo from a clay soil northeast of Ft. Collins. With the heavy rains that frequently accompany hail, it is often best to stay off the soil until it dries out to avoid further compaction. There is little you can do at that point anyway. Once soil dries, cultivation to break up crusts may be helpful.

Hoops for low tunnels with floating row cover fabric at the ready may offer some protection if you're on the spot to pull up covers when hail threatens. If hail stones are large, fabric may be shredded and protection value likely decreases.

Patience is a virtue after a hail storm. Once it is time to water again, consider weak fertilizer in the water to add to the stimulus for new growth delivered by the hail pruning. If plants aren't responding after a few weeks, remember the possibility of early July seeding of the 50 to 60 day vegetables for fall harvest.

Vegetable plants are resilient following hail and growers can only imitate that quality.

Photo credit: Hail damage on broccoli, Soil crusting following hail, Low tunnels and row cover fabric - All Carl Wilson

To Mulch or Not

2011-06-10T14:36:00.013-06:00

Vegetables are sensitive to environmental changes and the recent mix of hot and cold weather has had effects not just on transplanting warm season vegetables as mentioned last post. Some early season crops have already started to produce flower stalks. Remove and use the space to seed or transplant other vegetables maximizing production. Selecting a succession vegetable from a different plant family is good crop rotation practice.

If lettuce bolts for example, planting a rotational root vegetable such as carrot contributes to soil health as would adding compost before seeding. While carrots are easier to seed when weather is cooler, seeding is possible even in hot weather.

Carrots require 14 to 21 days to germinate. The chances of the seedbed drying out in this time are greater than with 7 days to germination seed. There is simply more time for something to go wrong whether it's windy weather or an irrigation problem that leaves soil dry.

Mulching with floating row cover fabric is one good solution for most seeded crops. To further increase chances of success with a many days-to-germination crop such as carrots, try doubling the mulch cover. Place grass clippings on top the fabric. Water easily percolates through both to wet the soil.

Periodically check under the fabric for signs of germination particularly once the 14 day mark approaches. Clippings are easily gathered when lifting the fabric and can be used elsewhere in the garden or in compost. Clippings alone generally are not used with carrots because they entangle with the ferny foliage.

As for mulching elsewhere in the garden in early June, definately avoid mulching peppers. It may be tempting to apply mulch during tranplant establishment but mulch delays soil warming. Wait until early to mid July to mulch peppers so soil thoroughly heats. This can make the difference between a good versus a poor or no harvest of peppers.

As for other warm season crops, it may be early to mulch them too. Efforts are probably better placed on proper watering and fertility to get plants established and hasten growth so they can outgrow flea beetle invasion that is common this time of year. More information on control of this insect can be found in the CSU Extension fact sheet, Flea Beetles.

Photo credit: Lettuce flowering, Seeding carrots, Double mulching with grass clippings over fabric - all Carl Wilson.

Pull the trigger on warm season transplants

2011-05-31T11:45:00.010-06:00

It looks like this will be the week that temperatures finally warm up for good along the Front Range making it safe to plant the warm-night loving vegetables. If you've been able to walk the tightrope between maintaining transplant condition while keeping them indoors at night and outdoors to harden on decent days, versus planting in the garden because they are too big, congratulations.

For those who have managed transplants to hold for planting this week, the warm nights above 50 degrees F should promote rapid establishment and growth. If you had to transplant last week or earlier, your plants may sit stunted for a while until they recover. Unfortunately this adds days to harvest to your tomatoes, peppers and other warm season plants.

While frost danger appears to have passed in Denver on May 2nd (31 degrees F), the night temperature was 33 degrees F on May 16. Although mostly in the forties and a few high thirties since then, it was still cold to think about setting out squash, peppers, tomatoes, eggplant and others.

Fertilizing transplants to keep them in good condition was helpful as long as this didn't cause too much new growth. A fully soluble vegetable fertilizer that contained phosphorous as well as nitrogen helped avoid purple backs to leaves, a sign of phosphorous deficiency.

Some plants that ran out of fertilizer could be turned around by fertilizing as these tomato transplants have been.

Photo credit: Fertilizing transplants, Phosphorous deficiency on tomatoes, Tomatoes turned around with soluble fertilizer - All Carl Wilson

Holding transplants

2011-05-26T14:05:00.016-06:00

With forty degree nights, growers are in a balancing act between how long transplants of very tender vegetables can be held versus planting and knowing they will be set back by the cold.

Many transplants may be running out of nitrogen as seen on the tomatoes in the top of this photo. These plants are starting to come back with addition of a soluble nitrogen fertilizer when watering. A product that also contains phosphorous is useful to avoid the purple backs of leaves seen with phosphorous deficiency. The tray of plants at the bottom of the photo received regular fertilization.

Don't apply too much fertilizer or you will end up with lanky growth. Of course these plants could be bumped up to pots larger than the 4 inch ones they are in but that is hardly desireable considering planting can hopefully be done in a week or so once nights are at least above 50, preferably 55 degrees F.

What can be done in the meantime while waiting for warmer nights?

Harden off plants by moving them outdoors on suitably warm days and back in at night.

If tramsplants are very tender cover them with floating row cover fabric while outside. This should prevent sunscalding until they've adjusted to higher light intensity and have hardened off.

Maintain enough fertility to keep transplants growing and leaves from turning yellow.

Remeber that transplants set out too early or transplants running out of fertilizer require recovery time which adds to the days to harvest time.

Keep blossoms pinched from plants. Now is not the time to set fruit as you want to keep them in vegetative growth, not flowering/fruiting growth.

Watch the weather forecasts for when night temperatures are predicted to be 50 degrees F or higher.

Transplant tender (not the very tender) transplants such as cucumber and summer squash that tolerate cool nights as long they are above freezing. Remaining cool season vegetable transplants such as chard, beets, romaine lettuce that will hold up better in summer heat, cauliflower, etc. can be put out (photo).

Finish any soil prep such as compost additions and build new beds while weather is cool to work.

Photo credit: Held tomato transplants, Planting cabbage, romaine lettuce, Swiss chard - Both Carl Wilson

Anxious to Plant

2011-05-20T20:04:00.007-06:00

Like everyone else, we are wondering when temperatures are going to thoroughly warm in order to transplant warm season vegetables to the garden. The five day forecast consistently shows "lows in the lower to mid 40's." For tomatoes and peppers, nighttime lows should be no lower than 55 degrees F.

The problem everyone is having is tomatoes stuck in the greenhouse getting leggy. Getting them out of a humid greenhouse where they can be put out on warm days and brought indoors into a non-greenhouse (drier) environment for night protection is ideal for hardening off. This should slow growth and curb leggy tendencies.

The outdoor part of this daily plant shuttle should have them located in a protected, short sun exposure location. Plants exposed to intense Colorado sun often sunscald because they have not developed the chlorophyll-protective plant pigments to shield them from UV and intense light.

One tomato plant brought to me this week for diagnosis showed the typical bleached, thin tan tissue typical of high light exposure. Transplants grown indoors during the cloudy spring weather we've had don't have the ability to stand up to the occasional clear day of intense Colorado sunlight.

Meanwhile, cool season vegetables such as this pak choy are happy growing in the cool, moist weather. The warm season transplants are just going to have to wait until Memorial Day weekend or later for the warm nights they require.

Photo credit: Greenhouse tomatoes and Pak Choy - Carl Wilson

Unique tomatoes and chiles featured at plant sale

2011-05-09T16:05:00.005-06:00

Vegetable gardeners looking for better plants can find them at the CSU Extension Plant-A-Palooza plant sale May 14. The sale features tomato plants from around the world and better chiles for chile lovers.

Tomatoes available include Azoychka, a Russian heirloom that produces yellow, 3-inch tomatoes in 70 days. It has a good acid content to balance its sweet, citrusy flavor. Zhefan Short is from the Zhengjiang province of China. This 68 day tomato produces pink 3 inch fruits with good sweet/acid balance in the juice. Stupice from Czechoslovakia is a prolific, early bearing red type with great taste. Other heirlooms will be available too.

The chiles featured are grown from seed acquired from the New Mexico Chile Pepper Institute. The Institute returned fifty year old seed lines to what they used to be before they wandered off-type in the last few decades. The bonus for gardeners is traditional heritage chiles that yield 10 percent more and have 20 percent more flavor.

Two chile types will be sold. ‘Nu-Mex Heritage 6-4’ provides consistent medium heat with good yield. ‘New Mex Big Jim’ produces a high heat level for those who like their chiles hot.

The Plant-A-Palooza plant sale fundraiser has long been known for heritage tomato transplants in addition to modern tomatoes, peppers, basil, perennials and annuals. The sale takes place on Saturday, May 14 from 8 am to 3 pm or sold out in Denver’s Harvard Gulch Park, 888 E. Iliff Avenue (at Emerson Street). More information at 720-913-5270.

Photo credit: Tomato transplants, Carl Wilson

Rain at last - more needed

2011-04-22T15:32:00.011-06:00

The official Denver precipitation total is now up to 0.84 inches for April (still 0.45 below normal for the month though). People closer the foothills received more rain during the upslope weather late in the week. Seedlings are coming up below the poly germination blanket (photo left) even without added sprinkling. See how to use this germination aid in previous post.

The name of the game now is to keep moisture on and through your soil. This is particularly true if you have added compost or turned under a winter cover crop for soil improvement.

Remember that the melding of the organic matter into the soil relies on microorganisms and they aren't active unless there is sufficient moisture. Turned under winter cover crops like rye and Austrian winter pea need a month to break down before planting vegetables IF the soil is moist enough for the microorgaisms to work over the buried plants.

Compost will release nitrogen during the growing season in addition to improving the structure of the soil. Again, soil moisture is needed for this to happen.

Check not only surface moisture, but also subsurface moisture content. After a dry winter, initial rains may have only moistened the top few inches. You may have to add supplemental moisture to wet the soil throughout the soil "profile." How does your soil moisture look down 6 to 10 inches?

Photo credit: Germinated seedlings under blanket - Carl Wilson

Dry spring weather

2011-04-11T11:36:00.008-06:00

Both low precipitation and frequent drying winds have dogged Front Range gardeners trying to germinate vegetable seeds this spring.

Many of the cool season vegetable seeds planted at the beginning of the season are small and can't be planted deep. These include broccoli, onions, lettuce, kale and radish. Being near the surface leaves them vulnerable to drying out during the days-to-germination period. If seeds start germination and then dry before emergence, they often perish.

What to do? In addition to frequent, light watering, the use of straw mulch or germination blankets can help. A useful germination blanket is spun polyester floating row cover fabric tacked down with wire U-pins. These fabrics gerenally allow 85% light transmission as well as passage of moisture through to the soil.

Blanket removal immediately upon seedling emergence is not mandatory and can be delayed until several true leaves have formed and seedlings are well established - that is if fabric is anchored loose enough to "float".

Photo credit: Floating row cover seed germination blanket, Carl Wilson

Vegetables 101 class

2011-03-18T12:56:00.005-06:00

The guiding hand of you, the grower, makes all the difference in adjusting growing conditions to achieve results. Come learn when and how to intervene to produce the vegetables you want for fresh eating and preserving.

Instructor: Carl Wilson, writer of Front Range Food Gardener

and CSU Extension horticulturist in Denver

For: Beginning to intermediate gardeners

Dates: Saturday, March 19, 2:30 to 4:30 p.m.

repeated Saturday, April 16 2:30 to 4"30 p.m.

Location: 200 Santa Fe Dr., Denver

Click to Register: Denver Urban Homesteading

Cost: $25

Photo credit: Seedlings in spring garden before thinning, Carl Wilson

Get Ready at Garden Symposium

2011-02-25T14:50:00.010-07:00

Get growing ideas at the Urban Farmers and Vegetable Gardeners Symposium scheduled for Saturday March 12 on the Auraria campus in Denver. The day includes presentations on specialty vegetable and fruit growing topics presented by the author of this blog, Carl Wilson, other CSU Extension personnel and Feed Denver instructors. You can choose six classes during the day from eighteen classes available as outlined below. For more information and to register, visit the Feed Denver website.

9:00
Connecting with Tasty Small Fruit - Joel Reich
Vegetable Seed Starting Secrets - Patti O'Neal
Sustaining Yourself in Changing Times - Kate Armstrong

10:00
Hear The Buzz - Bees and the Edible Garden - Beth Conrey
Lessons from the Vegetable Garden - Carl Wilson
Coming into Community through Urban Food - Kate Armstrong

11:00
Fruit Trees that Earn their Keep on the Front Range - Carol O'Meara
Tips and Tricks for Tomato Growing - Patti O'Neal
Urban Gleaning, Gathering and Foraging - Kate Armstrong

1:00
The Living is Easy Summertime Vegetables - Carol O'Meara
Troubleshooting Insects in the Vegetable Garden - Mary Small
Farming for Climate Change - Ariel Chesnutt

2:00
Vegetables are Cool in Spring and Fall - Carl Wilson
Healthy Soil makes the Vegetable Garden - Jean Reeder
Planting for Your Family's Food Needs - Sarah Marcogliese

3:00
Vegetable Garden Pests: More than Insects - Mary Small
Growing Vegetables in Small Spaces - Cathy Jo Clawson
Food not Lawns - Ariel Chesnutt

* Presented by: Colorado State University Extension, Feed Denver Urban Farms & Markets, Compost Auraria

Soil testing a good idea

2011-02-17T18:40:00.010-07:00

Now that the latest snow has melted, it's a good time to collect and submit soil for testing ahead of spring soil preparation and planting. Do be sure to air dry soil first before shipment.

I've seen both extremes over the years - too little fertility to produce good vegetables and over-fertilization that causes problems. Nationally studies show over-fertilzation is more of a problem in home gardens.

Excess nitrogen applied to tomatoes, squash and other "fruiting" vegetables produces luxuriant leaf growth and few fruit. With root crops such as carrot, turnips and parsnips you will see many leaves and small roots. Little nitrogen when corn tassels produces poor ear production.

Excess phosphorus tends to interfere with vegetables' ability to absorb iron and other micronutrients. The excess shuts down the roots production of phytochelates, organic molecules that increase iron uptake.

You can see that a general broadcast of a 5-10-5 or 10-10-10 fertilizer without knowing where you stand on fertility is likely a poor idea.

Sample prior to adding compost or fertilizer and send to the Soil Testing Lab at Colorado State University or another analytical lab for analysis. The soil test results will inform you about whether compost should be added and what type. For example a salt-affected soil with low organic matter will require low-salt compost (often plant-based and not containing manure).

Testing your soil on a three to four year cycle is usually enough to do a good job of managing the fertility and organic matter in Colorado soils. For more information check the Colorado State University Extension fact sheet Fertilizing the Vegetable Garden.

Photo credit: Collecting soil sample - Carl Wilson

Roots time

2010-11-20T17:24:00.012-07:00

With colder weather setting in Thanksgiving week, it’s a good time to explore your underground growing success by digging root vegetables. Beets are a good example, the cool weather causing them to be extra sweet.

‘Chioggia’ beets named for a town across the bay from Venice are pictured here. They are a 65 day, Italian home garden variety with festive red and white striped interior rings. Try them roasted with feta cheese. Sweet!

Carrots are another mainstay. ‘Nelson’ (pictured) is a half-long variety well adapted to growing in our shallow, clay soils. A Nantes type, it grows 5 to 6 inches long in 58 days. It consistently produces smooth, high quality roots with great uniformity.

Make fresh harvested roots a part of your November vegetable menu.

You can store roots in the garden longer into December and even January by covering them with a blanket of mulch. A foot deep layer of fallen tree leaves weighted with wire fencing or staked with netting to hold them in place should do the trick.

Photo credits: Dug 'Chioggia' beet root, 'Chioggia' beet slices, dug 'Nelson' carrot - all Carl Wilson

Garden cleanup

2010-11-04T16:02:00.026-06:00

Extended warm weather with many pleasant days has allowed ample time for garden cleanup. Though several hard freezes have killed warm weather crops, cool weather crops are still producing. If plants have overstayed their useful life, remove them. When cold-hardy cabbage family crops and others are finished, gather and dispose of all debris, preferably to the compost bin. If diseased or severely infested with insects, disposal off the property may be desirable.

One reason for a thorough fall cleanup is to avoid overwintering insects in your garden. For example, aphids overwinter as eggs as can be seen in the photo of kohlrabi, above right. Cabbage aphids (pictured left) and turnip aphids are the prime species found on cabbage family crops. Removing debris heads off an early spring aphid infestations. With some aphids on vegetable crops, it also eliminates the virus diseases that they can carry.

Photo credit: Cabbage aphids closeup (Brevicoryne brassicae) Whitney Cranshaw, Colorado State University, www.insectimages.org ; Aphid infested kohlrabi, Kale and kohlrabi debris, Raking debris – all three Carl Wilson

Hard freeze strikes late

2010-10-28T20:05:00.010-06:00

When the first widespread freeze finally came, it froze hard. Officially it was 20 degrees F at 6:30 a.m. at DIA. Considering the average first fall frost is October 7, the 28th of the month is nothing to complain about.

Hopefully you rescued what you could from the garden before the freeze. Somebody commented to me that tomatoes they’ve harvested in the last few weeks have had little flavor. Forty degree nights are flavor killers for this warm weather vegetable. It’s a good lesson in harvesting earlier for fresh use, or using the late proceeds in soups or sauces.

The squash and pumpkins should be in by now. This Carnival acorn is kind of spooky looking for Halloween and pretty ornamental in the garden. Good flavor too.

All that remains tucked in to the side of the frozen tomatoes are the cold-hardy greens such as kale, and the root vegetables such as carrots and beets. They will be good for another month or more. The root vegetables are particularly adapted for in-ground storage late into January if they are mulched.

Photo credit: Tomato harvest, Carnival acorn, Frozen tomato and pepper plants – All Carl Wilson

Pumpkin hints

2010-10-21T13:24:00.014-06:00

Many pumpkins seemed to mature early this year due to September heat. Pumpkins should be kept on the vines as long as possible IF the vines are healthy. If vines go down due to powdery mildew or frost, cut the handles from the vine to reduce shrinkage. This also avoids sunscald. Use hand pruners or long handled loppers.

Although we have had an extended period of warm weather, it will undoubtedly end soon. Pumpkins exposed to freezing conditions don’t store well. They should be harvested and brought indoors. You may have already brought them inside if they turned a solid orange and the rind was hard – a good move.

As long as pumpkins are starting to turn color, they will ripen and color off the vine. Recommended curing conditions are seventy degree days and sixty degree F nights. The area should be shaded, dry and well-ventilated. Remember that pumpkins for decoration are used through Thanksgiving so fruit late to color will still be useful. Cooking types can be cooked and frozen for later use.

Should you save seed from a particularly attractive pumpkin? Probably not since pumpkins cross readily with summer squash. Bees can carry pollen from as much as a mile away even if you don’t grow summer squash in your garden. Pumpkins don’t cross with fall squash.

Keep in mind that the pumpkins used for pies and eating, called sugar or pie pumpkins, have less water and better flavor than the strigy, Jack-o-lantern types. Most are a different species (Cucurbita moschata) as opposed to the decorative carving Jack-o-lantern varieties which are Cucurbita pepo. Grow different types of pumpkins for different purposes.

Check this “Pumpkin Eater” article by Shirley Perryman in the Food Science and Human Nutrition Department at Colorado State University for ideas about some novel uses of pumpkins and their health benefits.

What experiences did you have with growing pumpkins this year?

Photo credit: Pumpkin display, Pumpkins in garden, Just turning pumpkins harvested, Same green pumpkins ripened 3 weeks later - All Carl Wilson

Saving seed

2010-10-14T13:36:00.015-06:00

The desire to save seed is understandable particularly for people growing heirloom vegetables. It gives you more of a connection with plants you grow if you complete the seed to seed cycle. It can also be a connection to vegetables of your heritage, a contribution to preserving genetic traits for the future and perhaps could save you money on seed purchases.

First, the cautions. Don’t save hybrid seed because plants that grow from it don’t come true to type. In fact you will likely have all sorts of small to large plants and variable fruit in fruiting vegetables. F1 hybrid seed saving is a waste of time.

The self-pollinating vegetables are good bets for easy seed saving. They rarely cross with others of their kind and don’t need long distance separation or bagged flowers to prevent stray pollen from reaching flowers. Beans, peas, lettuce, tomatoes, peppers and eggplant are in this easy-to-save group. If you are growing ‘Brandywine’, ‘Cherokee Purple’ or ‘Mortgage Lifter’ tomato for the first time and like them, save seed if you are willing to grow your own transplants.

Open-pollinated varieties cross-pollinate but produce plants closely true to type if reasonably isolated by distance or time of flowering from other plants of their species. An example is ‘Straight 8’ cucumber. Wind-pollinated plants (corn) and insect pollinated plants (cucmbers, squash, pumpkins, melons) take more care to save because you have to pay attention to nearby plants and even hand pollinate.

Potatoes are popular heirlooms because tubers come true to type (no flowers involved). Baring disease accumulation in tubers, you can save colors and flavors not available in grocery stores. Examples are ‘Russian Banana’, ‘Yellow Finns’ and ‘Ruby Crescent Fingerling’.

Our dry Colorado climate is excellent for seed saving. Keep seeds in a cool place. Be sure to label with name, variety and date collected.

Share your seed saving tips and experiences with us.

Photo credit: Removing seed from ripe tomato, Flowering lettuce will produce seed - both Carl Wilson

Reflecting on garden efforts

2010-10-07T11:01:00.009-06:00

Warm weather lingers but plants are responding to signals that days are shortening. Summer squash plants that used to produce a fruit a day are down to one or two per week - this in spite of the record twenty-five days above 80 degrees F in September. Decisions will have to be made soon about removing declining plants and chopping them to compost.

It’s a good time to assess what worked and what didn’t this growing season. What varieties did well and which ones performed poorly? I am pleased with this yellow zucchini variety, ‘Soleil’ (photo left). It produced well and fruit had a good flavor in addition to a very bright yellow skin.

What about diseases and insects? The container tomato pictured maintained pale leaf color throughout the season. Leaves were small and stiffly held. Fruit were extremely slow to develop, ripen and lacked flavor. All these symptoms point to a virus that sapped the energy from the plant leaving it weakened. The lesson here is to avoid planting transplants that look off-color from the start or replace them early in the season as soon as unusual growth is noticed.

Some problems are hard to prevent. Psyllids were widespread this year on potatoes and tomatoes. Not all gardens were infested with these insects but enough were that it can be characterized as a severe psyllid year. Fortunately psyllids don’t overwinter here (except indoors) so next year insects might not find their way from southern areas resulting in no or little infestation. Both potatoes (affected foliage yellow in photo) and tomatoes (photo right with purple veins in leaves) are typically affected. See earlier psyllid article for more.

What did you learn from your vegetable garden this year?

Photo credit: 'Soleil' zucchini, Virus disease on tomato, Psyllid yellows on potato, Purple veins of tomato with psyllids - all Carl Wilson

Colorado’s fickle climate

2010-09-30T14:08:00.007-06:00

A few weather observations this week. The Colorado climate never ceases to amaze me. September 19 and 20 had record highs for those dates, 96 and 94 degrees F respectively. Then on September 23, some low lying areas in Denver and open space areas on the outskirts had light frosts overnight. The following weekend another 90 degree F record high was set on the 26th. Be ready - temperatures can change on a dime or so it seems.

A visiting gardener told me this week that his cucumbers and other frost sensitive garden vegetables froze on Labor Day, September 6, during the last cold snap. His garden is in a low lying area in south-central Denver, not even on the outskirts of town. Clearing nights with radiational frosts combined with air drainage into low lying areas can catch plants earlier than most of the surrounding area.

As they say in real estate – location, location, location. This savvy gardener hedged his bets by cultivating plots in several community gardens that were unaffected. These low lying areas are bad bets for growing fruit trees.

It’s a good time to think about frost protection and season extenders now that fall is officially here. I admit to being biased but one of the best discussions I’ve seen on these topics is our CSU Extension CMG Garden Note 722, titled Frost protection and Extending the Growing Season. Review it for a refresher on how measures such as plant covers are used best

Diagram from CSU Extension CMG Garden Note 722.

Harvesting and storing pumpkins

2010-09-23T15:08:00.007-06:00

Harvesting pumpkins seems pretty easy – wait until orange and detach from vine. It is and isn’t that easy depending on how long you want to store them.

Like many parts of the Upper Midwest, we seem to be having an early harvest season this year. Pumpkins and fall squash should be harvested when skin is tough and doesn’t yield to gentle fingernail pressure. Stems should be dry.

Research shows jack-o-lantern size pumpkins reach full color 45 days after fruit set and stems harden in 20-35 days after fruit set. This is for ideal growing conditions and may take longer if there is shade, drought, disease or other stresses.

Know that conditions both before and after harvest affect storage life. Vines that are healthy up to harvest make for a longer keeping pumpkin. Likewise, favorable storage conditions after harvest make a difference too.

Cut the stem with hand pruners to preserve stem health. Solid stems provide an effective barrier to rot. Use care in moving pumpkins to avoid nicks, scrapes and other mechanical injury. Move when the surface of the fruit is dry to be able to get a firm grip on fruit among other reasons. They keep better if harvested before frost and sustained periods under 40 degrees F.

Store in a shaded, dry area with good ventilation. The best storage temperature is 50 to 60 degrees F. This temperature is likely difficult for most people to achieve, particularly with hot weather lingering late into September this season.

Healthy fruit that is harvested and stored under favorable conditions can last up to 6 months. If you want fruit to last until Halloween, that is a reasonable goal. Storage until Thanksgiving will take a little more attention to each step of the growing and harvesting process.

Photo credit: Standard and flat French pumpkin types – both Carl Wilson

When are watermelons ready?

2010-09-16T14:55:00.001-06:00

I never used to be a fan of growing watermelons in northern climates. Years ago available varieties never reached maturity and tasted bland or green. Newer short season watermelons have changed all that. Varieties such as ‘Sugar Baby’ (75 days), ‘Shiny Boy’ (75 days), ‘Yellow Doll' (76 days), ‘Blacktail Mountain’ (70 days) and others have a reasonable shot at maturing in our short growing season. They should be transplanted like many warm-season vegetables so seed your own indoors in spring or purchase transplants.

A frequent question I receive is how to tell when watermelons are ripe. You can gently roll the melon over to check for a yellow groundspot. Another clue is to look for the curled tendril below the vine attachment. Green tendrils indicate a green melon while a shriveled, brown tendril indicates maturity.

Then there is the sounding method. A knuckle tap that yields a dull sound indicates under-ripe. If it sounds hollow, the watermelon is ripe for eating. A soft sound indicates over-ripe. This method also works in the produce market.

Tapping knuckles takes on a whole new meaning for cool vegetable gardeners.

Photo credit: Watermelon on vine – Carl Wilson, ‘Shiny Boy’ watermelon – 2010 All America Selections winner.

Plan now to ripen tomatoes

2010-09-09T17:30:00.000-06:00

The first week of September brought four nights with temperatures in the forties to Denver. Tuesday morning following the Labor Day holiday I was surprised to find frost on the grass in the open space area near me in Southwest Denver (no frost in the residential area nearby though). Seasons change quickly on the Front Range making this a good time to plan to get the most from summer tomato growing efforts.

Newly setting tomato blossoms, small and very green fruit won’t mature in the remaining growing season and are best pruned off. New, vigorous shoots also may be clipped back. Don’t remove an excessive amount of leaves as these supply nutrients to fruit. Light pruning directs plant energy to fruit that has a chance of maturing.

When fruit set is heavy, it can work against gardeners. Ripening numerous fruit takes a lot of energy from the leaves and tends to delay the whole crop turning red. If there are only a few weeks before frost and fruit is not ripening, try removing some of the mature green fruit to ripen what’s left on the vine.

Cooler September temperatures help fruit to ripen because the red tomato pigments, lycopene and carotene, are not produced above 85 degrees F.

As late September approaches, gardeners often try to extend the life of their plants by covering with cloth or plastic. Covering plants works well for nearly red tomatoes, but not as well for mature green ones. Research shows that chilling injury on green fruit occurs at temperatures of 50 degrees and decay losses are heavy on fruit exposed to 40 degrees F. Red ones well on their way to ripening better tolerate colder temperatures.

Before frost hits and plants go down, pick and bring fruit indoors to ripen. Extended exposure to cool temperatures interferes with ripening and flavor development. Clip fruit to leave a very short stem piece but not so long to punch holes in other tomatoes. Stems ripped out of fruit will open them to decay.

Eliminate young, green fruit, as research shows it’s more likely to spoil than ripen and never develops the flavor consumers want anyway. Mature green fruit will develop good flavor. Mature green tomatoes are well sized and have turned light green to white.

Sort and store fruit in groups that will ripen at similar speeds. Fruit may be “mature green”, "turning" with a tinge of pink to "pink" with 30 to 60 percent color showing, "light red" with 60 to 90 percent color present, and others "fully red" but not soft.

Store ripening tomatoes at 55 to 70 degrees F. Refrigerator temperatures of 40 degrees are too cold to ripen mature green tomatoes and are colder than desired for ripe ones. Ripening enzymes are destroyed by cold temperatures whether in the garden or in a refrigerator.

Ripen tomatoes in well-ventilated, open cardboard boxes at room temperature checking them every few days to eliminate those that may have spoiled. Mature green tomatoes will ripen in 14 days at 70 degrees F.

Cold weather and frosts can come in late September before typical October killing frosts arrive. Plan now to realize the biggest harvest from your vegetable garden.

Photo credit: Roma tomato with mature green fruit, Staked tomatoes, Tomato harvest in box - all Carl Wilson

Harvesting and ripening pears

2010-09-01T16:01:00.013-06:00

The best way to tell when fruit is ready to harvest is often the simple taste test. For backyard gardeners not concerned with shipping fruit, this is good advice for apples, peaches, plums and grapes.

Pears are the exception. “Tree ripened” pears will not be satisfactory. Pears left on trees ripen from the inside out and stone cells fully develop making for “gritty” eating. When the outside is ready, the inside is often brown mush. If picked slightly immature, they ripen uniformly with a smoother flesh consistency OFF the tree.

Harvest most European pears such as ’D'Anjou’ (photo above) and 'Bartlett' when they easily detach from trees. Tilt them upward to horizontal and they come loose when ready for harvest. ‘Bosc’ pears (photo right) are always difficult to separate from the tree and stems may have to be clipped with a sharp pruner. All pears should feel hard when picked.

In looking for signals for when to harvest, disregard the red blush on varieties that develop it such as D'Anjou (photo above). The ground color of the pear skin will change to more closely resemble the mature pear of that variety. With Bartlett, D’Anjou and other yellow pear varieties, skin becomes a lighter green.

Pears then have to be ripened indoors. Some pears such as D'Anjou require cold storage before ripening. Bartlett does not but 2 days of chilling may help even ripening. D’Anjou and Bosc should be chilled for 2 weeks in the refrigerator away from apples, onions, potatoes and other fruits and vegetables. Pears in grocery stores and those shipped by specialty mail order companies have already been given their chilling treatment.

Ripen at room temperature, 65 to 75 degrees F. Warm temperatures of 85 degrees F or higher interfere with ripening. Bartlett pears generally ripen in 5 days, Bosc in 7 days and D’Anjou in 7 to 10 days. The longer pears are chilled, the shorter the ripening time when removed from cold storage.

Pears naturally produce ethylene gas inside the fruit as they ripen. You can shorten ripening time by placing pears in a closed paper bag with a ripe banana or apple, both of which produce ethylene to speed ripening.

Pears are ready to eat when the flesh just below the stem yields evenly to gentle pressure.

Photo credit: d'Anjou pears, Bosc pears - both Carl Wilson

Tomato fruit cracking

2010-08-26T15:40:00.008-06:00

Some tomato fruit are cracking now that we’re in the midst of tomato ripening season. Stem end cracks can be of two kinds but are both due to the same causes. You may see cracks that spread outward from the stem (radial cracks see photo right) or concentric cracks in circles with the stem in the center (photo left).

Cracks generally appear as fruit is maturing (mature green or coloring), rarely when small. The earlier fruit cracks, the deeper cracks become.

Growth cracks can be traced to rapid changes in environmental conditions, either moisture, temperature or both acting together. Dry weather followed by heavy rains is known to cause cracking in many tomato varieties. The strength and ability of the skin to stretch vary by variety and thus some varieties are marketed as “crack resistant.” They are worth a try if you have had problems.

High nitrogen fertilization stimulating rapid growth is also a cause for cracking. Slow release granules, organic sources or low strength fertilizers (soluble types in water) should be considered for fertilizing now.

Cherry type tomatoes are problematic for growth cracking. They are so small that when cracks occur they often run down most of the fruit (photo right - click to enlarge). Harvesting fruit before it turns dead ripe eliminates the possibility that further growth on the vine will result in cracks.

Do everything you can to even out the water to avoid growth cracks; irrigate not too much and not too little. Mulch soil to prevent rapid summer evaporation and dry down. The cherry tomatoes pictured are growing in a large container where it is always difficult to maintain even moisture in spite of daily watering.

Although gardeners can modify fertilization and watering practices, they can’t change the temperature. Temperature fluctuations and our dry air that toughens skins are probably big reasons we have cracking problems. Our average day-night temperature fluctuation for August has been 29 degrees F. That’s a wide range of temperature for a plant to handle.

Photo credit: Radial cracking - Carl Wilson, Concentric cracking - Iowa State University Extension, Cherry tomato fruit radial cracking - Carl Wilson

Telling powdery mildew by its spots

2010-08-19T13:21:00.009-06:00

Powdery mildew can be a chronic late summer and fall disease in the vegetable garden. I’ve found that some people mistake the normal color variation in leaves for the disease. Many squash have silver-white blotches like spots on a leopard. See photo of the normal blotches on the leaves of the All America Selections winner, ‘Papaya Pear’ squash right.

When squash becomes infected with powdery mildew, the dusty flour appearance of the disease looks more irregular and is on the surface instead of being part of the leaf. See photo left. Note that the disease appears on the upper leaf surface, not leaf undersides. Infected leaves can turn yellow, become distorted and fall prematurely (photo below right).

The severity of the disease depends on many things including plant variety, age of the plant, health status of the plant and weather conditions. Young, succulent growth is more susceptible than older plant tissue. Avoid late summer applications of nitrogen fertilizer.

Powdery mildews tend to be severe in warm, dry climates. High relative humidity is needed for fungal spores to germinate once they land on leaf surfaces. Shaded sites with poor air circulation favor disease. This is another reason to grow in open, full sun locations. These sites promote plant health by having ample sunlight for photosynthesis. They also ensure that humidity around leaves is quickly dispersed by adequate air movement.

Ground applied (drip) watering rather than overhead sprinkling also helps humidity control. Water in the morning rather than evening to take advantage of sunshine that quickly dries leaves.

If these cultural controls are not adequate, supplement with chemical applications of potassium bicarbonate (preventive) and neem oil (eradicant after infection). Read all label instructions and make sure the product you purchase is labeled for use on squash.

Photo credit: Healthy ‘Papaya Pear’ squash leaf, Powdery mildew infestation on squash leaves, Severe infestation and leaf yellowing – all three Carl Wilson

Peaches – what a haul

2010-08-11T13:11:00.014-06:00

This is one of those years when we are reminded what peaches can really do. We only see peach fruit production like this in maybe one year out of five on the Front Range.

Because we don’t see peach fruit every year due to blossoms freezing in the spring, people may not know how to handle or prune trees. Excessive fruit loads will commonly break limbs in heavy bearing years. Propping up limbs (photo right) is a poor solution because limbs rub and damage bark when moved in the wind.

Preventing broken limbs goes back to June with fruit thinning, removing excess fruit when they are thumbnail size to leave only one fruit every six inches on limbs. This is what commercial peach growers commonly do and results in larger and sweeter fruit (fewer “packages” for the tree to sweeten up).

What can you do when limbs break? Not much, unfortunately but use a pruning saw to remove jagged edges and smooth the branch tear on trees. Basic pruning to wide angled scaffold limbs helps. Limbs at wide angles to the main trunk are much stronger than narrow angles.

As for fruiting wood, peaches produce only on one year-old twigs. The branches producing fruit this year should be removed in winter. Peaches are pruned hard removing the older, thicker branches to leave productive, young twigs (this year’s growth). Trees that aren’t pruned rapidly become dense and produce poorly. Light reaching producing branches is necessary to grow fruit.

For more details on peach pruning, see this post. Mark your mental calendar now to prune this winter!

Photo credit: Weighted down peach branch, Propped branch, Loaded peach tree – all Carl Wilson

It's raspberry time

2010-08-05T17:45:00.013-06:00

In spite of nearly every tree fruit escaping spring blossom-killing freezes and bearing well this year, small fruit remain more certain to produce yearly crops. Red and yellow raspberries are the most reliable. Black raspberries are not widely recommended because of lack of cold hardiness; however roots do survive to try producing fruit again in two years time. This may change as better adapted and more reliable black raspberry varieties are introduced.

If several red and yellow raspberry varieties are planted, you can realize a harvest from midseason to frost. Summer-bearing Nova, Killarney and Boyne produced crops in July and now the fall-bearing types Anne( yellow), Autumn Britten (photo above right) and old standby, Heritage are ripening and can produce up till frost.

Raspberries are naturally a biennial, growing canes one year and producing fruit on those overwintered canes the summer of the second year. The problem comes with overwintering canes. In most parts of the Front Range this usually isn’t a problem. With summer bearing types, you wait until the canes are finished fruiting in the summer of their second year to remove them.

Post WWII breeding produced the fall-bearing types that grow canes and produce fruit in the same season, With no canes to overwinter, harvests are more assured and pruning is easier since they are simply cut to the ground after the fall harvest.

What are the problems with raspberries? Homeowners often ask why their raspberries that once produced well fail to bear a crop anymore. Raspberries will last about ten years and bear best in the first five years of that period. After that accumulated viruses carried in by aphids decrease production. The planting should be removed and new stock planted. Don't get plants from fellow gardeners because of viruses. Buy virus-free stock from reputable nurseries. Plant in new soil that has been amended with organic matter and drainage ensured often by building a raised soil bed.

More raspberry information is available in the CSU Extension raspberry fact sheet. Give them a try.

Photo credit: Autumn Britten fruit, Raspberry canes, Carl Wilson

More butterflies than usual?

2010-07-28T21:00:00.023-06:00

Is it just me or are many of you seeing more butterflies than average this summer? I also think I’m seeing fewer European paper wasps, a major predator of butterfly larvae. Perhaps that’s why.

The adults and larvae of butterflies require different food plants. The larvae of cabbage worm eat cabbage family plants (photo of damaged kale left, larva photo right). The white adult butterflies gather nectar from a variety of flowering plants (adult on thistle below left).

Control of cabbage worm includes the use of the natural bacteria Bacillus thuringiensis Kurstaki strain. See the CSU Extension fact sheet on Bacillus thuringiensis for advantages and disadvantages of using this natural control. Another idea is to exclude the adult butterfly from laying eggs on plants with the use of a floating row cover (photo right).

A colorful butterfly plentiful throughout the Denver area this season is the Two-tailed swallowtail. Adults (photo left) feed on geranium, thistle and milkweed plus other flowers, larvae (photo right) consume green ash and chokecherry. Gardeners curious about the yellow butterflies flying by can now rest easy knowing the larvae are not eating their vegetables.

To learn names, see photos, and find out the food plants for the adult and larval stages of common Colorado butterflies, see the CSU Extension fact sheet on butterflies in the garden.

Photo credit:
Cabbage worm damage to kale, Carl Wilson
Cabbage worm larva, Whitney Cranshaw, CSU Extension
Adult cabbage worm butterfly, Davud Cappaert, Michigan State University
Row cover, Carl Wilson
Two-tailed swallowtail adult, CSU Extension
Two-tailed swallowtail larva, Whitney Cranshaw, CSU Extension

Seed now and watch for cutworms

2010-07-15T14:25:00.020-06:00

Now is the time to plant seeds of late summer and fall crops where earlier ones have been harvested. Chose 60 day or less crops (carrots, beets, bush beans, radishes, Swiss chard, New Zealand spinach) or ones that like to mature in cooler temperatures (lettuce, peas, spinach, kale, collards, Asian greens). Note that a nice option with greens is that they can be harvested at almost any stage of maturity in the event of a short growing season.

With a temperature in the nineties F, small seed will be hard to germinate Use seed germination fabric and water lightly but frequently.

One seed germination hazard that some people think is a spring but not summer pest in cutworms. Cutworms are caterpillars that cut and kill tender seedlings round the soil line.
The notorious "miller moth" that people in our area recognize in the adult flying form (photo above left) is Army cutworm in its larval caterpillar stage. (See above right photo).

Note that there are also climbing cutworms as the person who brought chomped basil leaves in for diagnosis today discovered. Beet armyworm (see photos adult left and larva right) is a climber active in mid to late summer that chews on a very wide variety of plants. Variegated cutworm is another (photos below).

Cutworms typically feed at night and hide in soil cracks, under dirt clods or seek other cover during the day. If you are going to find them, you have to go out after dark with a flashlight.

Cutworms are preyed upon by ground beetles, rove beetles, spiders, tachinid flies, parasitic wasps and other garden insects as well as toads and snakes. If natural enemies aren’t providing sufficient control, consider your weed situation. Cutworm moths are attracted to weeds for egg-laying.

Promote rapid seedling growth with good cultural practices (right amounts of water, loose soil, proper planting times, etc.) and use transplants. Transplants and older plants aren’t as tender and less likely to be damaged at the soil line. Note that climbing-type cutworms will find the tender leaves on top.

Protect tender transplants and seedlings with cutworm collars (cardboard, foil) or milk carton rings. Insecticide baits are available for cutworms. They are more targeted than whole-plant sprays which may kill beneficial insects as well as pests. Note that B.t. (Bacillus thuringiensis) natural insecticide is generally ineffective against cutworms.

Photo credit: Miller moth Whitney Cranshaw, CSU Extension; Army cutworm larva Frank Peairs, CSU Extension; Beet armyworm adult Merle Shepard & Gerald Carner & P.A.C. Ooi; Beet armyworm larva Frank Peairs, CSU Extension; Variegated cutworm adult Ian Kimber; Variegated cutworm larva Charles Olsen, USDA APHIS PPQ.

Mind the herbicides

2010-07-09T17:24:00.007-06:00

Use caution in using herbicides because injury to vegetable gardens is always a concern. Common ways herbicides reach vegetables are vapor movement from nearby properties, drift of sprays and through imported manure or straw mulch.

Growth hormone type herbicide injury causes leaf feathering, cupping, stem twisting and sometimes produces compressed growth resembling a cobra’s head (also called fiddlenecking). Tomatoes (see photo left) are particularly susceptible but other vegetables can also be affected (eggplant photo right).

2,4-D is commonly used for spraying dandelions and other broadleaf weeds. Ester forms are more likely to vaporize and be carried by wind than amine forms. Vapor clouds can drift for surprising distances depending on weather conditions. Granular formulations rarely volatilize.

High temperatures above 85 F during or immediately following applications increase the possibility of vaporization. Spraying earlier in spring, during cooler periods in summer and at cooler times of day is recommended. Follow label directions dealing with temperature.

Sprays should be adjusted so droplet size is large because fine sprays have a greater potential to drift. Use lower pressures or sprayers with large orifice nozzles that increase the average droplet size. Mind wind movement and chose calm days for spraying. Use spray shields when using products such as glyphosate (Roundup and other brands) near gardens. Do not apply insecticides with a sprayer used for weed killers.

Another way herbicides can reach vegetable gardens is in residues on straw used for mulch or through manures dug in as soil amendments. Clopyralid can be moved this way. This herbicide is not used for broadleaf weed control in landscapes but is used in pastures, crop production and rights-of-way among others.

Clopyralid is very persistent in manures, composts and soil. It can damage sensitive vegetable plants in extremely small amounts. Sensitive plants include those in the bean family (beans, peas), sunflower family (lettuce, endive, globe artichoke), and especially the tomato/potato family including eggplant and peppers.

Know your source or try imported straws and manure on a test plant in a pot before using in your whole garden.

Photo credit: Tomato and eggplant herbicide injury - both Carl Wilson

Tomato-potato psyllids watch

2010-07-02T14:17:00.009-06:00

Psyllids are insidious insects that cause a plant condition known as psyllid yellows, the result of a toxic saliva injected by the insect. Be on the lookout for these insects on your tomatoes and potatoes now.

Insects are reported to be heavy in the Arkansas Valley and adults have been found in sweep nets in Fort Collins. Psyllids do not overwinter in Colorado and migrate from overwintering sites in southern TX, AZ and NM. Reports from the southern part of the state are tip offs to be on the watch for them. Outbreaks are erratic depending on winds and weather conditions. They can also be transported on transplants.

Watch for the eggs and nymphs. Eggs are small (one-thirty second inch), orange-yellow and supported by small stalks. Beneficial lacewings have similar eggs but are larger, white and on longer stalks. Psyllid eggs take 6 to 10 days to hatch into nymphs.

The nymphs look like flat plastic discs attached to the backs of leaves or on stems (photo above right). They are yellow at first but become green and well camouflaged as they mature. The nymphs don’t move once they settle down to suck plant juices. They excrete small, waxy beads of white “psyllid sugar” (photo left) as they feed for 2 to 3 weeks.

The adults are rarely seen and are green at first but rapidly turn dark Adults fly to new plants to lay eggs and 4 to 7 generations are produced in a growing season.

Symptoms on potato and tomato plants are similar. Yellowing or purpling along leaf midribs and leaf edges is concentrated in top leaves. As the disease progresses, the yellow-green or purple-red color spreads to the entire top growth and growth slows. New top leaves often remain small and tend to stand upright giving the top an almost feathery appearance.

When psyllids attack tomato plants early, effects can be so severe that little fruit is set. Infestations later in the growing season on larger plants cause only a small yield loss. If psyllids attack potatoes before tuber set, many small tubers form. Later attacks reduce growth and cause irregularly-shaped potatoes that may sprout prematurely underground before harvest.

Because insects are small and don’t attract attention due to being stationary and camouflaged, they go unnoticed before the damage is well underway. Watch on a regular schedule for psyllid sugar and turn leaves over to look for nymph “discs” (photo right). If found, take action right away.

Do all you can (fertilize and water regularly) to get plants growing vigorously early. Insecticides labeled and available to homeowners are permethrin and esfenvalerate products. An alternative is sulfur dust if leaf undersides can be coated. Two percent insecticidal soaps provide useful if more erratic control.

Psyllids infest but cause insignificant damage to other vegetables in this same family, eggplant and peppers.

Photo credit: All photos Whitney Cranshaw, Colorado State University entomologist

June vegetable growing notes

2010-06-24T11:06:00.010-06:00

Although late this year, the weather is at last consistently warm. The cold, fifty degree highs of the June 12 to 13 weekend marked the last of lingering spring and days finally yielded to warmer temperatures. Cool season vegetables are bolting (seed formation photo right) and warm season vegetables are taking off. Nighttime temperatures are out of the forties, and the fifty some degree nights are even skirting with sixty degrees F. It’s time to think about early summer vegetable gardening tasks.

Fertilize to size tomatoes and peppers – After transplants are established and growth really starts, it’s time to fertilize and encourage plants to put on size. This early growth builds the frame to bear a decent fruit load. In mid-summer fertilization should cease because you want the plants to enter a fruiting mode and not produce vegetative leaf growth.

Seed those 60 day’ers– June is the time to seed or continue to succession seed a variety of vegetables for summer. Carrots, beets, chard, collards beans, squash, New Zealand spinach, and others are all fair game. Many of these are 60 days or less to harvest.

Thin – Once seeds have germinated, do take care to thin seedlings by pinching, cutting or pulling out. Crowded plants won’t produce good yields. Seeds such as beets are really a dried fruit that contain multiple seeds and the germinated cluster of seedlings must be thinned (photo above left). Snip the plant to be removed at the soil line with a scissors to avoid disturbing the roots of the seedling meant to be left to grow. Beet thinnings can be used for salads.

Water – Consistent watering is coming into play big time. You can cut back from the post-transplant babying of plants into a more normal, twice-a-week routine (in clay soils – more frequently if growing in sandy soil). Check soil for moisture and only allow plants to get three-quarters dry before watering. Note that many people overwater tomatoes according to national studies.

Mulch – Now that temperatures are in the nineties and soils are thoroughly warm (68 degrees F at last check), mulching should be considered. Herbicide-free grass clipping mulch is my favorite (photo right). It’s readily available on a weekly basis with lawn mowing, quickly biodegradeable when it’s eventually mixed into the soil, and performs all the usual mulch chores of keeping down weeds, holding in moisture, keeping soil surface temperatures cooler for root functioning, etc. Apply in two installments 5 to 7 days apart with each fresh layer being no more than 1 to 2 inches thick to avoid matting, rotting and associated odors. The total cumulative mulch depth should be no more than 2 or 3 inches thick.

Photo credit: Bolting lettuce, Beet seedling clusters, Grass mulch – All Carl Wilson

Year of added fruit tree maintenance

2010-06-21T13:30:00.008-06:00

In many years untimely freezes leave fruit trees with little or no fruit on the tree. Not this year. Even though the first half of May was cool and had two more days than normal below freezing (7 total), the temperature on those coldest nights only dropped down to the 28 degree F limit during bloom and early fruit formation.

Limit because 28 degrees F is the lowest temperature that fruit trees generally can withstand before damage to the crop occurs. This year proved that right as there are bumper crops of most fruit including apricots, peaches, cherries, plums, pears and apples.

With a heavy fruit set come responsibilities. June is a good month to consider fruit thinning if the tree hasn’t taken care of this itself through the “June drop.” Peaches, apricots and apples should be thinned to 6 inches apart on the limbs when fruit is thumbnail sized. The photo right shows peaches in need of thinning (this should have been done when they were smaller). With apples, and pears this prevents codling moth worms from traveling between snuggled fruit and damaging two apples instead of one (photo below left).

Thinning helps fruit grow to a larger size and avoids later limb breakage from too heavy fruit loads. Cherries aren’t generally thinned. Be sure not to remove the spurs (short bearing stems) when you thin the fruit on pears, plums (not always thinned) and spur-type apples. Peaches bear directly on twigs with no spur involved.

For codling moth control to prevent wormy apples in apple and pear, thin fruit, trap insects and time insecticide applications appropriately. Insecticide applications should have begun right after petal fall. Permethrin and carbaryl (Sevin) are the most common homeowner treatments which are generally timed for 10 to 14 day intervals.

Click on this link for information on dealing with apple and pear insects.

Look here for information on managing peach tree borer, the most destructive insect of cherries, peaches and plums.

Photo credit: Heavy peach set, Apple cluster - both Carl Wilson

Pruning grapes

2010-06-10T21:03:00.007-06:00

It’s tough to answer a question from homeowners on how to prune the American grapes we grow in this area. The first roadblock is their mental picture of California grape vineyards with spur-pruned grapes trained to a head or cordon. This isn’t the way American grapes should be pruned.

American grapes don’t produce fruit next to the main trunk. Instead of European wine grape-style pruning to 2 or 3 buds, we leave 6 to 18 buds because of the vigorous American vines. The more vigorous the variety such as ‘Concord’, the more buds can be left.

The second dilemma in answering the how to prune question is that vines are usually already sprawled over an arbor or pergola. Making any sense out of vine structure and counting buds isn’t realistic at this point. I advise the “clear dead canes out and prune live canes to keep the vine on the arbor approach.”

With the vigor of these American vines, pruning wrong is awfully hard to do because rank growth will take care of any pruning “mistakes” if there is such a thing. The real mistake is not doing any annual pruning at all. In some form this usually meets the two real viticultural pruning objectives of shaping vines to meet gardener’s needs and balancing fruit production with vegetative growth.

The vines shown in the photo top left contained dead canes from the previous season. They were recently pruned to remove dead wood and clear the way for this season’s growth (obviously well along). Two varieties are grown on this arbor, ‘Concord’ and ‘Himrod’. The two “after” photos right show the arbor after pruning and the amount of dead wood cleared out.

What are your thoughts about how to prune and the harvest results you’ve gotten with your method? Please tell us where you live and what grape variety you’re growing.

Photo credit: All 3 photos Carl Wilson.

Warm season finally arrives

2010-06-04T14:00:00.008-06:00

Whew! It was great to finally get the transplants off the porch and into the garden on Memorial Day weekend. Even then nighttime temperatures were only high forties – still a little cold for tomatoes and peppers.

The first half of May was very cool in Denver. Although it didn’t freeze past the average last frost date of May 10, the nights were cold. People wanting to transplant early had to provide season extenders such as water walls for nighttime heat.

Those transplanting without season extenders once again proved the wisdom of waiting two to three weeks past the average last frost date. Only by then had the weather settled and cold winds turned warm. I had questions about why peppers and tomatoes weren’t growing from people transplanting early in the month. The answer is cold nighttime temperatures under 50 degrees F.

Now it looks like daytime temperatures will reach close to 90 degrees F with nighttimes in the low 50’s – perfect for warm season vegetables. This is typical of our high and dry steppe climate, going from cold to hot in a short period of time.

Continue to seed those 60 day root crops. Even though beet seed is larger than carrots (photo), I use germination fabric over both to keep the seedbed moist and increase germination percentage. It’s a great tool particularly on 90 degree F days when soil dries out so fast.

Photo credit: Protecting transplants, Transplants in garden, Beet seed - all Carl Wilson

Banner year for fruit set

2010-05-27T16:56:00.007-06:00

It looks like a banner year for fruit set based on an informal look at fruit trees and conversations with Front Range fruit tree owners. Apricots and peaches may set fruit in an average of 2 years out of 5 and they both have fruit this year. Later blooming cherries (see photo left) and apples bloomed when temperatures were above 28 degrees also escaping freezes when in bloom.

The danger now appears to be too heavy a fruit set. Peaches tend to set fruit too heavily and should be hand-thinned when fruit reaches 1 inch in size. Space fruit 6 inches apart (see photo). Apricot fruit should be thinned the same way and thinning will produce larger-sized fruit just like peaches.

In a heavy-set year, we inevitably get July and August phone calls from people whose home peach tree limbs have broken from the heavy fruit load. Remember that peaches only bear on 1 year old wood and bearing branches will be removed at the end of the season, leaving this year’s branch growth to bloom and produce fruit in 2011.

Apples are not always thinned but could benefit from thinning in the case of heavy set (photo left). Natural “June drop” is typical in heavy fruit set years but may not always thin fruit enough. Thin in June to 6 to 8 inches or to every other spur. Break up clusters leaving only single fruit. DO NOT remove the long-lived spurs, only the fruit. Thinning fruit produces larger fruit.

Sour cherries also have spurs that produce for 2 to 5 years. Clusters are not generally thinned. Sweet cherry trees are less favored for the Front Range and not as hardy as sour cherries and other stone fruits. Branches can winter kill.

Photo credit: Cherry bloom, Peach fruit thinning, Heavy apple set - All Carl Wilson

Spring weather - hardening off transplants and bees

2010-05-20T17:16:00.002-06:00

Two things have been frustrating about our spring weather. It’s been hard to put transplants outdoors to harden off. The days when temperatures have been over 55 degrees F or that winds haven’t blown have been few. Exposure to the outdoors helps leaves toughen and some plant movement thickens stems.

Note that there is a marked difference between the light intensity outdoors versus near a window indoors, as much as a hundred fold increase. The plants in the photo went from low indoor light to bright sun. They should have been placed in the shade outdoors as an in-between step. Even outdoor shade is considerably brighter than indoor light. The plants reacted to the bright light by turning white, indicating a breakdown of green chlorophyll (photo-oxidation). Gradually acclimating plants to brighter light is another reason to “harden-off” plants in stages lasting only an hour or two – if the weather allows.

Then there is the poor honey bee. They have gotten off to a rough start. Fall conditions were poor for them to set up stores for surviving the winter. Bloom was late this spring and though it is abundant now, the weather has usually been too cool for foraging. All and all this has been a stressful time for colonies and predictions are that many probably starved out.

In addition to weather, there is the worrisome problem of colony collapse disorder. Nationally, initial results from a survey by the USDA Agricultural Research Service and Apiary Inspectors of America show managed honey bee colony losses of 33.8 percent over the winter. Last year losses were 29 percent. These continued high losses are causing fears of poor crop pollination. Gardeners can do their part by planting bee-attractive flowers and avoiding the use of pesticides particularly during bloom periods when bees are active.

Photo credits: Solarization of tomato, Carl Wilson and Honey bee, Jack Dykinga

Spring 2010 review and outlook

2010-05-13T11:20:00.001-06:00

Spring 2010 has been favorable for growing cool season vegetables seeded in late March or early April. Temperatures in April were near normal and not warm in Denver. Watering was necessary to overcome the many dry weeks of the month with the April 21 to 25 rain/snow upslope that left 2 inches of precipitation being the exception.

The first two weeks of May were cool (5 degrees below average) and dry (0.75 inches below normal) until the May 11-12 storm left over an inch of moisture. Fertilization and consistent watering of greens and developing vegetables were needed to maintain vigorous growth and quality.

The goal now should be to harvest spring crops as they reach best quality and mature them before the onset of hot temperatures. Whether higher temperatures arrive as early as late May or in June, bolting (seedstalk development) of spring greens and deterioration of quality will quickly follow. The semi-hardy vegetables can be planted in early to mid May including beets, carrots, parsley, parsnips, cauliflower and Swiss chard.

Plans should be made and seed and transplants purchased to follow spring crops with warm season vegetables. The first to go in are the tender vegetables including beans, corn, cucumbers, New Zealand spinach and summer squash. Transplants of cucumbers and summer squash should be delayed until the time for planting the very tender vegetables the end of May. Soil germination temperatures and daytime air temperatures should be consistently above 60 degrees F for this group. The soil temperature on May 10 was 53 degrees F (Ft. Collins data).

The very tender vegetables include melons, pumpkin, winter squash, eggplant, pepper, tomato and lima bean. This group is intolerant of frost as well as cool day and nighttime air temperatures below 55 degrees F. A daytime temperature of 60 degree F or higher is needed for growth. They should be planted when weather has become summer-like and the cool breezes of spring are past – at least two weeks after the last frost date (May 10 is average last frost date in Denver). They can be planted earlier with water walls or similar devices to provide nighttime heat and frost protection. Transplants are available at the Plant-A-Palooza plant sale May 15 .

Gardeners can make a difference

2010-05-04T13:28:00.005-06:00

There is no more powerful combination than growing vegetables and generosity.

The Plant A Row for the Hungry effort urges gardeners to grow something for themselves and something to feed others. In Denver, the effort kicks off May 15 at the CSU Extension plant sale. Starter kits will be available for the first 100 people willing to plant vegetables to donate to Food Bank of the Rockies agency sites.

The plant sale is from 8 a.m. to 3 p.m. at the CSU Extension offices in Harvard Gulch Park, 888 E. Iliff Avenue. The sale features heirloom and modern tomatoes, hot and sweet peppers, other vegetables, basil, annuals and perennials. Plant flowers that attract bees alongside your squash, cucumbers, melons and other vegetables to make sure they are pollinated for good yields.

Starter kits include free vegetable and herb seeds donated by Botanical Interests, Plant A Row markers, Echter’s Garden Center coupons and other fun gardening items. You can double the pleasure you get from gardening by donating food to feed others in addition to eating food you grow yourself.

Transplant growing

2010-04-29T11:25:00.014-06:00

Transplants being produced for setting out in mid to late May should be well along by now. The peppers in the photo are being grown for sale at our Plant-A-Palooza fundraiser. They are the improved chile types described in the recent “Back to the Future” article about chile seed that was cleaned up to be the more productive and flavorful peppers they used to be. Information on the sale is in the top right corner of the blog.

It’s been hard with recent cold/warm weather punctuated by rain/snow to move transplants outdoors during the day for a dose of sunshine. Even when day temperatures have been above 55 degrees F for peppers and tomatoes, it’s often been excessively windy. While mild wind is fine for promoting strong stems, gales are not.

Shuttle homegrown transplants outdoors on warm, calm days and bring them in before temperatures cool too much in late afternoon. This acclimates plants to drier air and UV light, helps build thicker stems with flexing from wind movement, and provides higher light intensity than generally available indoors. Leave plants indoors when air temperatures are in the low 50’s or below. Of course transplants of cabbage and other cool season crops will withstand cooler temperatures. Many of these should have been set out and already out of the house.

Do balance light and temperature to promote growth with adequate fertilization for good plant color. Avoid excessive fertilization which produces lanky, succulent growth. Watch for golden yellow lower leaves that indicates the need for nitrogen fertilizer and for purpling suggesting the need for phosphorous (photo left).

Between timing seed planting to have the plant the right size to set out, manipulating the environmental light and temperature conditions, and regulating fertilizer nutrients, growing transplants is an art as well as a science.

Photo credit: Chile pepper transplants, Phosphorous deficient tomato - both Carl Wilson

Winds don’t defeat seed germination efforts -

2010-04-15T14:07:00.001-06:00

Wind, wind go away! If you regularly check this blog you might have gathered by now that I’m a big fan of germination fabric. With all the recent windy days, I thought the lettuce, kale, kohlrabi and other small seed I planted might not germinate. It seemed like the surface soil was drying out faster than I could replace it with once or twice a day watering.

Indeed I wasn’t sure the fabric would stay in Colorado and not end up in Kansas. This in spite of being secured with wire U pin anchors punched through the fabric into the soil plus heaps of soil piled on the edges. I got good germination, thank you, as you can see from the photos of lettuce seedlings left and the familiar notched leaves of cabbage family plants right. I know I couldn’t have achieved that germination percentage if it weren’t for the fabric.

Shallow planting to avoid burying seed and surface moisture for germination (wetting top ¼ to ½ inch) are critical to getting seedling emergence.

The next challenge is to keep seedlings moist enough to develop a root system and grow. After that they can be weaned from light, frequent watering to less time intensive every two day and then every three day watering. Gradual changes in watering frequency are best to avoid stressing plants. Keep them actively growing to preserve quality.

Photo credit: Lettuce seedlings and kohlrabi seedlings, both Carl Wilson

Seed warm season crops indoors now

2010-04-09T14:00:00.006-06:00

It’s now 7 weeks out from the May 31 traditional Memorial Day transplanting date for warm season crops into the garden. Even though the Denver last frost date is approximately May 10, many gardeners wait until the end of May when weather is more stable to set out tomatoes, peppers, eggplant, squash and more.

If you plan to grow your own transplants, 6 weeks before transplanting is generally sufficient for tomatoes and 8 weeks for peppers. Have the soil in pots warm (70 to 75 degrees F is ideal) and grow in a warm room, not cold basement. One advantage we have in Colorado is many days of bright sunshine so growing in a sunny window is doable even without a greenhouse.

A guide for seeding and transplanting vegetables into the garden based on outdoor soil temperatures follows (see last week for soil temperature details and on-line soil temperature readings link):

Garden soil temperature and planting times
35 degrees F – lettuce and onions
40 degrees F - peas, radish, spinach, cabbage
50 degrees F – tomato, pepper, corn
55 degrees F – beans
60 degrees F – cucumbers, squash, eggplant

Photo credit: Peppers seeded and growing in window - Carl Wilson

Time to seed early vegetables

2010-04-02T15:10:00.004-06:00

A check of soil temperatures today showed 41 degrees F. That’s warm enough to seed cool season crops such as lettuce, onions, peas, radishes, spinach, cabbage, broccoli and kale in an open garden. (Those using coldframes could beat this planting date by a month or more.)

Soil temperatures should be measured at 4 inches deep at 8:00 a.m. If you don’t have a soil thermometer, you can follow the on-line readings taken at the weather station on the Fort Collins campus of Colorado State University.

Once seeded, you may want to cover with a germination blanket (photo above) to keep small seeds moist until seedlings emerge and even for a week or so afterwards. Our sun, wind and dry air at mile high elevation rapidly dry the surface of soil. This material, anchored with soil at the edges or U pins of bent wire punched through the fabric, helps the surface stay moist. It’s sold as floating row cover or seed germinating fabric at garden centers.

Even with a fabric cover and cool temperatures, at least daily watering likely will be necessary during the days to germination period generally listed on the seed package. In addition to proper planting depth (avoid seed burial deeper than recommended), maintaining consistent moisture is the biggest factor in successful seed germination.

Photo credit: Using seed germination blanket, Carl Wilson

Hold your spring soil prep enthusiasm

2010-03-24T15:06:00.006-06:00

If you didn’t prepare soil in the early part of March when it was dry, think twice about when to do it now. Two snowstorms on the 19th and 23rd (see raised bed photo right) each left my Denver garden with an inch of water, 2 inches total in less than a week. Heavy, spring snows can bring a lot of welcome moisture to gardens when snow melts (photo below left) but can interfere with cultivating soil.

Clay soils are especially sensitive to tilling at improper moisture content. They should be tilled at medium moisture, not too wet and not too dry. Tilling when too wet can create clods that take years to disperse on some clay soil types.

To check moisture, take a handful of soil and gently squeeze into a ball. If the ball crumbles when poked with a finger, it can be tilled. If the ball only reshapes with the pressure of poking, it’s too wet. Wait for it to dry more. With some clay soils there may be only a few days when soil is at the proper moisture content. If spring snows or rain are frequent, planting may be delayed.

Very wet soils are also easily compacted. Stay out of the garden when soil is wet. Water acts as a lubricant allowing soil particles to more easily slide over each other. Don’t compact soil that you worked so hard to make loose by walking in a wet garden.

One other moisture related matter is worth mentioning. Wet soils warm more slowly because the sun’s energy is used in evaporating water rather than in raising soil temperature. Cold soils will delay planting further.

Photo credit: Snowy spring raised bed gardens, both Carl Wilson

Turn under winter cover crops

2010-03-13T15:08:00.017-07:00

If a winter cover crop of rye or Austrian winter pea was planted in the fall, turn it under a month before planting or seeding. I turned my winter rye under this past weekend adding “green manure” to the soil.

The large soil critters such as the earthworm pictured here (below right) and soil microorganisms will “chew” through the raw roots and tops over the next weeks for soil improvement. I left the soil “rough” and certainly didn’t step on and compact it. That’s an advantage of raised bed gardening – standing outside the bed to work your soil. It will not be tilled again when seeding or planting so the soil structure can be preserved as much as possible. More tilling would simply destroy it and there is no good reason for it.

First, why do you need to wait a month before planting? The living critters working over the plants consume soil oxygen and can create plant health problems if not tilled in ahead of time. Once the bulk of the “raw” plants have been consumed, the soil environment stabilizes and lack of oxygen for plant root growth is no longer a problem.

Second, it’s about more than the buried plants. If it was only the plants we could find a way to chop them into fine pieces and instantly improve the soil. The secret is what the soil critters add to the mix and the squeamish need read no further. Simply know that without them, you couldn’t realize the soil structure and fertility improvement benefits from planting and turning under cover crops.

Large and small critters feed on the buried plants adding substances such as slime, mucus and fungal mycelia. Analyzing these substances show things such as gums, waxes and resins which glue soil particles together. Clumped particles enhance the tilth, porosity, and water holding capabilities of soil – all good things for healthy plant growth.

Take care of your vegetable garden soil and it will take care of you.

Photo credit: Two soil spading photos - Carl Wilson

Late dormant season fruit tree pruning

2010-03-09T09:07:00.001-07:00

Before buds break in March, prune dormant fruit trees. Recently I helped prune peaches in a Denver community garden (unpruned peach photo left). Peaches must be pruned hard every year as they only bear fruit on one year old twigs. Renew them yearly by pruning to replace nearly all fruiting wood. Two year old or older twigs are unproductive.

The photo left illustrates how hard this pruning should be on peaches (pruned branch left, unpruned tree right side of photo). You should end up with a skeleton of thick, blunt scaffold limbs sprouting very few thin, one year old twigs (photo right). Leave bearing twigs of 12 to 18 inches in length removing the shorter ones (bear small fruit) and longer ones (bear too many and are subject to breakage).

Twigs pointing upward and out at 45 degree angles from horizontal are most productive. Remove vertical and downward pointing twigs. “Stacked” twigs or branches growing over top one another shade the lower twig so remove one of them.

Prune trees to allow light into the center of the tree. With fruit trees, light equals fruit. Dense, unpruned trees will yield poorly. Remove dead and interfering branches, renew fruiting wood, and control size to keep bearing wood close to the ground.

Maintain a zone of equilibrium between excess growth (the rank growth tendency of the top of the tree) and poor fruiting (lower portion tendency). Do this by pruning harder in upper, outer portions of a tree to allow light in. Most home gardeners tend to prune mature trees too little.

Finally, remember that pears, cherries, apricots and most apples bear fruit on short spurs that last for some years. This is very different than peaches so don’t prune off the short spurs or you will have no crop.

Here’s hoping that spring freezes spare our fruit tree blossoms so we can have a good fruit crop this year.

Photo credit, All peach pruning photos, Carl Wilson

Vegetable Gardening 101 class

2010-03-03T10:39:00.012-07:00

Learn the keys to successful vegetable growing on the Front Range including tips and tricks to make your gardening life easier. Colorado’s climate realities include a short growing season, cool summer nights, dry air, erratic late spring and early fall frosts. Soil conditions add another gardening challenge. The guiding hand of you, the grower, makes all the difference in altering growing conditions to achieve results. Come learn when and how to intervene to produce the vegetables you want for fresh eating and preserving.

Instructor: Carl Wilson

For: Beginning to intermediate gardeners

Dates: Saturday, March 20, 2:30 to 4:30 p.m.
repeated Saturday, April 10 same times

Location: 200 Santa Fe Dr., Denver

Click to Register: Denver Urban Homesteading
Cost: $25

Photo credit: Plant starting under lights, Carl Wilson

Consumer sources of garden information

2010-02-25T11:10:00.005-07:00

Consumers are mining the internet for more and more garden information. If you are online reading Front Range Food Gardener, exploring online seed catalogs and university plant information websites, you’ve helped vault the internet from fifth to second most used source for garden information in the last year.

The national Garden Trends Research Report just released by the Garden Writers Association Foundation asked “Which of the following are your sources of gardening information?” Consumers rated top sources to be friends (43%), internet (29%), magazines (22%), books (22%), retailers (19%), newspapers (13%), blogs (7%) and other (18%).

I always urge people to look at the source of the information. Anyone can throw up a website or blog so look for who is writing. Is it a credible university, nursery, plant society, government agency or similar source?

There are certainly knowledgeable amateur gardeners but critically think through their recommendations and interpretations before buying their information. You can always run your own experiment and try growing one plant their way and one “normally” to see if there is any difference.

Do check if they are writing about plants in your hardiness zone and environment. This is why Front Range Food Gardener is localized to Denver and other Front Range Colorado cities. Our climate is challenging. While experiences elsewhere can inform us, they always need to be interpreted for how well they translate to our environment and soils.

Low elevation humid climate plant growing even in the north doesn’t always copy to high and dry plant growing in Colorado. Likewise growing in acid eastern U.S. soils doesn’t mean plants will perform similarly in alkaline Colorado soils.

Check back for more garden information and share your garden experiences on this blog. Note your city location so others can interpret how well information applies to them. We can all help each other be more successful food gardeners.

Vegetable varieties for high elevation Front Range areas

2010-02-15T16:10:00.018-07:00

Larry Stebbins of Pikes Peak Urban Gardens recently spoke at the green industry ProGreen conference at the Colorado Convention Center. His favorite vegetable and herb varieties are listed below. If they grow at Colorado Springs elevations, they must be special. Varieties mentioned first in bold type are favorites. Other adapted varieties follow. If a variety is new to you, try it this season.

Artichoke Globe: Imperial Star (annual, 85 days from seed)
Asparagus: Jersey varieties
Basil: Genovese, Sweet Basil
Beans: Kwintus Pole, most bush varieties (Blue Lake, Tendergreen), Kentucky Wonder Pole
Beets: Detroit Dark Red, Bulls Blood, Chioggia
Broccoli: Premium Crop, Pacman, Early Dividend
Cabbage: most all, try Chinese varieties
Carrot: Mokum, Ya Ya, Kaleidoscope, Nelson, Danvers Half Long, Burpee A#1, Sugarsnax
Corriander: Santo
Corn Sweet: Bodacious, Ambrosia
Cucumber: Cool Breeze, burpless varieties
Garlic: Spanish Roja, Inchelium Red, Chesnok Red, Chet’s Italian
Kale: Red Russian, Redbor
Lettuce: Buttercrunch, romaines, leaf lettuces, mesclun mixes
Mustard: Osaka Purple, Mizuna
Onion: Candy, SuperStar White, Red Candy, Lisbon White Bunching, Copra, First Edition, Red Zeppelin
Parsnip: Hollow Crown
Peas: Sugar Ann, SugarSnap, Oregon Sugar Pod(snow pea), Garden Peas (Maestro, Wando and Marvel),
Pepper Sweet: Carmen, Green Bell (most varieties), Fooled You Jalapeño
Pepper Hot: Mexibell, Anaheim, Big Chile, Jalapeño, Mucho Nacho, Garden Salsa, New Mex Joe Parker
Potato: Russet, Yukon Gold, Red Norland
Radish: Cherry Belle, French Breakfast
Rutabaga: Laurentian
Spinach: Giant Noble, Tyee, Space, Melody, Bloomsdale
Squash Summer: Magda, zuchinni (most varieties), yellow, crookneck,
Squash Winter: Early Butternut, Table King or Table Ace Acorn, Buttercup, Spaghetti
Swiss Chard: Ruby, Rhubarb, Bright Lights, Neon, Fordhook
Tomato: Big Beef, Sweet Million or Sweet 100’s, Celebrity, Fantastic, Early Girl, Better Boy, Mortgage Lifter, Sweet Baby Girl

Chile peppers - back to the future

2010-02-03T10:28:00.009-07:00

If you love to grow chiles and eat Mexican food, you will want to know about New Mexico State University’s Chile Pepper Institute. They have cleaned up the ‘Big Jim’ and ‘6-4’ chile varieties to yield 10 percent more and have 20 percent more flavor! The resulting heritage varieities are what these chiles used to be like before seed lines wandered off type. The fruit grown from CPI’s seed more closely resembles the flavor many may remember from years ago – and higher yield is an added bonus.

Do you have trouble maturing chiles in your shorter growing season area? You will be interested in NuMex Espanola Improved, a variety adapted to fewer days to maturity growing.

See the CPI Shop 2010 catalog for seeds as well as books and posters. Note also that they carry more than just chile peppers. Sweet, paprika, jalapeno, Cuban, Caribbean, ornamental and many other types of pepper seeds can be found in their colorful catalog pages. Pepper enthusiasts can also get the T-shirt and salsa.

CPI’s online catalog is fun to browse even if you have no thoughts of growing peppers this season. Before you know it you may just find a pepper that you have to try in your garden.

Photo credit - Caged pepper plant- Carl Wilson

Blueberry growing intense in Colorado

2010-01-12T10:00:00.003-07:00

by guest writer Joel Reich*

Many Colorado gardeners have long lamented their inability to grow blueberries (Vaccinium corymbosum and related species). The problem stems from the fact that most of Colorado’s soils are slightly to highly alkaline, above pH 7.0 (neutral). Blueberries must have acid soils (a pH of about 5.5) in order to thrive. Unfortunately, there is just no practical way to manage Colorado soils in order to produce a pH that low.

The good news for blueberry lovers is that, with extra effort, there is a proven way to grow delicious blueberries in your Colorado garden. The keys to success are 1) plant the blueberry bushes in a medium that is primarily (or entirely) composed of sphagnum peat moss. This readily available material has a pH of approximately 5.5, so it is perfect for blueberries. Two further keys to success are: 2) make sure that the root zone always stays moist (even during warm, dry spells in winter), and 3) protect the bushes from drying winds during the winter. This can be done by wrapping the bushes with burlap or old sheets while they are dormant.

Any planting method that incorporates these three key elements should lead to success, so feel free to be creative. For those who want an established recipe for success, follow the instructions below. Keep in mind that you will need to have at least two blueberry plants of different varieties (for cross-pollination purposes) in order for the plants to set good crops.

For each plant:

- Dig a hole that is 20” deep, 30”long and 20” wide.
- Get a plastic-wrapped bale of sphagnum peat moss (3 cubic feet).
- Punch about a dozen holes in the bottom of the plastic wrap.
- Drop the bale, holes down, into your pre-dug hole. You can grow more plants in a row by dropping multiple bales in a trench. Different plants are necessary for cross-pollination as noted above.
- Cut an 8”x 8” “X” in the plastic on top of the bale and fold back flaps.
- Plant a bare-root blueberry plant directly into the peat moss (Do this in early-mid April).
- Re-close the “X” using tape, leaving about a 3” hole in the middle to accommodate the trunk of the bush.
- (optional) Install drip irrigation line by cutting a small hole at either end of the bale and feeding the line through the holes, resulting in an irrigation line that runs on top of the peat but under the plastic.
- Fertilize in early May and early July with a balanced fertilizer for acid-loving plants (i.e. Miracle Grow for Acid Loving Plants).
- Water and provide winter protection as discussed in keys to success above.
- Provide protection from “critters” as animals love blueberries too.
- Enjoy blueberries year after year!

* Joel Reich is CSU Extension horticulturist at the Boulder County Extension office in Longmont, CO where he trials blueberries and other small fruits.

Photo credit: Dladek

Grow your own chicons (Belgian endive)

2009-12-16T11:30:00.005-07:00

Growing delicious salad greens in December in Colorado may seem a stretch to some but it’s not as far-fetched as it may seem. Belgian endive or witloof chicory will produce the tight shoots of leaves known as chicons through winter forcing. They are highly desired for gourmet salads and are used either alone or with other greens. They can also be lightly steamed and are high in vitamin C.

As discussed last post, this plant is another form of chicory, Cichorium intybus. Belgian endive requires a two stage production process. These plants are grown as a root crop during the summer (first stage), dug and stored cold for winter forcing (second stage). They require a little over 3 months for root production so plant in early July. Be sure to plant Belgian endive and not the endive/escarole/frisee seed discussed last post.

Roots can be dug after the first frost in fall depending on variety and maturity. Mature roots are 1 ¼ to 2 ¼ inches in diameter. The final harvest should be made by early December from beds mulched to avoid soil freezing. Trim tops back to 1 inch and store roots by planting in pots of dry soil or lined out in rows in open-top trays that are at least 6 inches deep and have drainage. Roots that are too long for the container can be trimmed from the bottom. Do not water after planting but make sure that soil touches all sides of the roots and air pockets are eliminated. Store in an uncovered coldframe or under an outdoor deck on a north or east side where temperatures will hold at 40 to 60 degrees F (cooler is better). Root cellars or unheated garages and garden sheds are other storage possibilities. Roots are often covered with perlite, sawdust or dry sand after soil temperatures have cooled. This keeps them cool but mulches them from extreme cold.

The mulch becomes necessary to the second stage growing process, forcing. Roots should be forced in the dark so the shoots remain yellow-white and develop a mild flavor. Light cause the shoots to turn green and taste bitter. Some home growers use a length of 4 inch diameter plastic pipe over a root planted in a pot, filling the 6 inch tall pipe with perlite or a peat-sand mixture. Containers can be watered by applying water to the soil surface at the base of the pipe and not through the top of the pipe. Keep roots moist for the 3 to 4 week forcing period. Good soil drainage is important so roots don’t rot. Harvest when shoots poke out the top of the pipe. With this pipe method, you can tip the perlite or peat-sand mixture out of the top of the pipe, lift the pipe off the shoot, and cut the chicon at the soil line.

Winter forcing can be done over time producing a stream of fresh greens. Limitations to production will be when storage becomes too warm and roots start to grow. Note that traditional varieties such as ‘Totem’ and ‘Witloof di Bruxelles’ are forced by the soil or mulch covering method in darkness. New hybrid varieties from Europe such as ‘Normato’, ‘Mitado’ and ‘Tardivo’ produce tight heads in darkness without the need for soil or mulch covering.

Photo credit: Witloof roots, Rasbak. Chicon, David.Monniaux.

Frisee – Gourmet chicory greens

2009-11-25T16:22:00.007-07:00

Chicory (Cichorium intybus) is an interesting garden vegetable that has many forms and is known by many names including frisee, curly leaf endive, flat leafed endive or escarole, radicchio, Belgium endive, witlof and chicon. Qriginally from Europe, chicory is a weed in America with scattered plants growing in Colorado at 4000 to 7000 feet elevation. Many people think it is a native “wildflower” (see photo). It is often confused with blue flax which has one layer of petals instead of the double “wheel” of chicory flowers.

Of the selected forms for eating, the leafy vegetables include frisee sometimes sold by seed companies as Cichorium endivia. The frilly leaves (see photo) are used as a bitter fresh green in salad mixes. Flat-leafed endive (escarole) is more often used as a wilted or cooked green. Note that some people use the term frisee for frilly lettuce but lettuce is in a whole separate genus, Lactuca. The chicory group of plants is confusing enough without mixing the idea of lettuces in with them.

It’s entirely appropriate to be talking about frisee in late November as the greens are very cold hardy and can survive until early December particularly if mulched. Frisee is easy to grow in 45 days and can be planted in mid-summer for a fall crop, or in early spring as a cool season crop for harvesting before hot weather arrives. Some people blanch their crop by tying leaves in a bundle 3 days before harvest to deprive the inner leaves of light and change them to a light yellow color.

Next post will be about another fun thing to do with chicory plants - harvest roots and force the gourmet witlof (chicon) buds to grow in winter.

Photo credits: Cichorium intybus flower-Alvesgaspar, Frisee – Frank C. Muller

Leftover vegetable seed storage

2009-11-12T18:58:00.011-07:00

Many home gardeners end up with a few seeds in a seed packet or even unopened packets of seeds. Are they worth storing for planting next year?

A dry climate is ideal for storing many vegetable seeds. Life is extended under dry conditions even if seeds are stored at warmer temperatures of 70 degrees F and not 32 degrees F. Exceptions are bean and okra seeds that develop hard coats causing poor germination. Seeds will reach 4 to 7 percent moisture under the 20 percent humidity often seen in Colorado.

Here is a relative guide to the life expectancy of seeds stored under favorable conditions. Use it for deciding whether to keep or toss leftover seed.

Life expectancy in years
Bean 3
Beet 4

Broccoli 3
Brussels sprouts 4
Cabbage 4
Carrot 3
Cauliflower 4
Chinese cabbage 3
Collard 5
Corn 2
Corn salad (mache) 5
Cucumber 5
Eggplant 4
Endive 5
Kale 4
Kohlrabi 3
Leek 2
Lettuce 6

Muskmelon 5
Mustard 4
New Zealand spinach 3
Okra 2
Onion 1
Parsnip 1
Pea 3
Pepper 2
Pumpkin 4
Radish 5
Rutabaga 4
Salsify 1
Spinach 3
Squash 4
Swiss chard 4
Tomato 4
Turnip 4
Watermelon 4

Photo credit: Seed packets, Carl Wilson

October snow dump

2009-10-29T14:09:00.007-06:00

Did you lose your garden? Mine is somewhere under the 18 inches of white stuff in the photo left. What good moisture for us! In dry Colorado, you never object to moisture however it comes (even if you secretly wish it to be doled out a little more gradually). This snow event will probably end up yielding about 1.5 inches of moisture when it melts this weekend. It’s predicted to be in the 50s F so the white will be a passing thing.

In addition to the moisture, snow is a good insulator. I’m not too worried about my annual ryegrass cover crop (photo right) that is coming up or my kale and other fall crops. They should be fine and the moisture will give them a boost.

Gardening resurgence in New Zealand - Like us, gardeners in the southern hemisphere are getting on board the trend towards more vegetable growing in the worldwide recession. See the news from the “kiwis.”

Photo credit: Snow in garden and Annual ryegrass - Carl Wilson

Evaluate tomato performance

2009-10-23T16:03:00.002-06:00

Before memories fade, now is the time to evaluate what tomato varieties performed well for you this season.

The tomato variety that performed best in my southwest Denver garden was ‘Yellow Taxi’ (64 days, photo left) This was followed by the widely adapted All American Selection, ‘Celebrity’ (70 days). ‘Large Red’ (heirloom 82 days), ‘Sun Cherry’ (58 days) and ‘Green Zebra’ (heirloom 75 days) were poor performers. All were sorely tested by the July 20 hailstorm that hit the western Denver Metro area. ‘Yellow Taxi’ and ‘Celebrity’ recovered and produced.

The cool, early summer this year affected all Front Range tomato gardeners. Longer season varieties struggled more than others. Keep in mind that if you have part day shade, your days to harvest becomes longer because it takes 1 ½ of your part shade days or so to chalk up one day on the published days to harvest rating. For you, choosing short days to harvest varieties is a must.

What tomato varieties performed well for you in 2009? Make your notes to guide your choices in future years. Share your experiences with our readers and help everybody. Do note your location in your comment.

Photo credit: ‘Yellow Taxi’ tomato fruit, Carl Wilson

Last plants left standing

2009-10-14T19:45:00.021-06:00

Wow. It was a cold and sustained hard freeze the end of last week. The low in Denver October 9th was 18 degrees F. The high on October 10th was 26 degrees F and low that night 17 degrees F. Both the high and low temperatures for Saturday the 10th were record low readings for that date. The photo right is of kale and lettuce under an inch of snow in my Denver garden that Saturday.

Even with a day and a half of readings below freezing, some hardy vegetables amazingly survive. Lacinato kale and onions, Purple Vienna kohlrabi and purple cabbage (photos) are still going strong. So are lettuce, radishes and hardy herbs such as parsley (photo). The root vegetables underground are also fine.

Now is the time to be glad you made those early July plantings of fall crops. You can be enjoying your garden until Thanksgiving.

Photo credit: Kale and lettuce under snow, Lacinato kale and onions, Purple Vienna kohlrabi, Purple winter cabbage, Parsley - Carl Wilson

Cold doesn't end garden chores

2009-10-09T12:06:00.014-06:00

I overheard someone in the barber shop say how quickly cold weather arrived this year. If you’ve lived in Colorado for very long, you know that the unexpected is the rule. The arrival of snow in the third or fourth week of September is not unheard of. I saw the first snow-rain here on October 8 this year.

The usefulness of covering plants will come to an end this week as night temperatures dip into the low twenties F and hard freezes prevail in most areas. Covers help with a few degrees under freezing but not with temperatures this low and repeated over several nights. Some of the hardiest vegetables such as kale, cabbage, peas and parsnips may survive. (Red Russian kale shown with frost on leaves above left, and two days later unharmed above right).

If you have automatic drip or spray irrigation for your garden, it’s time to be concerned about freezing of exposed backflow prevention devices. Until you are ready to get the water blown out of the device for winter, some precautions may be in order depending on how exposed the backflow device is (photo left). Wrap an old rug for insulation, pull a plastic yard bag over the wrapped device for waterproofing, and cinch with duct tape to prevent wind from ripping it off (photo right). This will generally get you by for a short period.

Do plan to remove killed tomato, squash and other warm season vegetable skeletons after a hard freeze. You can avoid overwintering many vegetable diseases and insects by doing a thorough fall cleanup.

Early blight fungus overwinters on diseased plants and some weeds. Remove diseased tomato plant debris and clear weeds from the garden. If the disease was severe, consider moving tomatoes to a new location next year if you have this option. The unusual bacterial spot seen this year also survives on plant debris.

Viruses that affect tomatoes such as Tomato spotted wilt and Impatiens necrotic spot cause yellow rings or spots on fruit. If you see these, remove plant debris because viruses survive in plants, not soil. Note that lettuce, pepper and weeds such as bindweed and nightshade will harbor viruses.

Thrips insects that spread viruses from plant to plant overwinter as pupae in soil crevices or on plant debris. Flea beetles that chew shotholes in leaves spend the winter as adults hiding under leaves, dirt clods and other protected sites.

Fall plant cleanup and fall tillage tend to disrupt all of these pests.

Photo cedit: Two kale (frozen and two days later) and two backflow preventer (open and wrapped) photos, Carl Wilson

Extending the season in fall

2009-10-01T11:47:00.012-06:00

The decision about what action to take with impending fall frosts can be complex. That’s probably why many simply throw a cover over their warm season crops (peppers in photo, tomatoes, etc.) and hope for the best.

The rhythm of the seasons with shortening days and cooler temperatures really speaks against fighting the trend. Harvesting tomatoes and letting them ripen indoors as discussed in the September 17 post may be a better choice in many ways. Cold temperatures destroy flavor and chilling injury decreases “shelf life” of the fruit leaving them open to decay. Room temperature indoors eliminates both problems.

Tomatoes will not be setting more fruit in cool temperatures so saving green plants is not productive from that standpoint. Concentrating on soil improvement by removing warm season plants to the compost bin and planting a cover crop as discussed last week may be a better use of a gardener’s energy.

Cool season greens planted in mid-summer (kale and mesclun in photo) tolerate frosts well. They may be more productive for the water applied in fall than warm season plants. Maturing root crops will also survive initial frosts and store well in the garden until dug for use.

Covers can perform well in radiational frosts experienced under clear nights. Cloth (photo left) will trap soil heat with the plants and is fine as long as it doesn’t get wet. Wet cloth loses heat due to evaporative cooling. Plastic traps heat and doesn’t have evaporative losses due to moisture but must be removed promptly the following sunny day to avoid cooking plants. Do remove any cover the next day to allow the sun to warm the soil again.

See CSU Extension Garden Note on Frost Protection and Extending the Garden Season for more extensive information including comments on use of space blankets and Christmas tree lights under covers.

Photo credit: Plastic to cover peppers, mid-summer planted greens, fabric covered tomatoes, all credit Carl Wilson

Winter garden soil improvement

2009-09-24T18:24:00.003-06:00

Vegetable garden soils ideally should contain 5% organic matter. If your soil is lacking, boost it during the winter season by planting a cover crop.

Cover crops are grown to produce green organic matter to turn under the soil. Along the Front Range, plant them from September to no later than mid-October. In addition to boosting organic matter, they prevent wind and water erosion over the winter, build soil structure and suppress weeds.

Legume cover crops can add nitrogen to the soil through the action of nitrogen fixing bacteria. It is good practice to buy rhizobium (beneficial root-associated or “rhizo” bacteria) and apply as specified if the seed is not rhizo coated. Rhizobium bacteria are specific for the legume species and are sold with a specific expiration date.

Broadcast the seed/rhizobium mix at the specified seeding rate and water to germinate. If irrigation systems are shut down, hand watering in the fall will help the crop establish before growth slows for the winter.

Winter ryegrass is often used alone as a cover crop (see photo). Winter rye/Austrian pea or a winter rye/hairy vetch mixture overwinter well in Colorado. Winter rye is a quick germinating and pioneering grass. Hairy vetch is a hardier legume than winter pea for the coldest areas. Seed winter rye and Austrian pea at 4 to 6 ounces per 100 square feet. Plan on 2 to 3 ounces of hairy vetch seed for each 100 square feet of garden area.

Note that these green winter plants are attractive to deer and geese. If they are well established prior to extreme winter temperatures, plants generally recover from winter grazing in spring.

When turned under, the decomposing green material can deprive spring vegetables of oxygen if not done far enough in advance of planting. Plan to mechanically till or hand spade under at least two weeks and better yet a month prior to planting. The legumes may have to be tilled several times to kill them and prevent resprouting.

Many gardeners do not have the land area to plant a cover crop for the growing season without depriving themselves of vegetables for a year. Winter cover crops solve that problem.

Consider planting a cover crop this winter to improve your soil.

Pick and ripen tomatoes when frost threatens

2009-09-17T17:08:00.005-06:00

While warm weather can linger well into September along Colorado's Front Range, temperatures can also drop unexpectedly. The earliest September freeze in Denver occurred on September 8, 1962 when the temperature dropped to 31 degrees F. I’m certainly hoping for a warm fall but will be prepared to mount a tomato “rescue” if things look dicey.

Covering plants to trap heat from the soil is often enough to get through a short one or two night situation. Extended days of cold particularly when accompanied by cooling moisture (rain or snow) are more problematic. In those cases, harvest fruit before the frost event and ripen indoors.

Pick fruit with even a hint of color. Also harvest green tomatoes with a glossy green appearance that are at least three-fourths of their full size. Remove stems. Wash fruit under a stream of water and allow to air dry on clean towels. Make immediate use of any damaged fruit and save only blemish free tomatoes for ripening.

Low humidity causes fruit to shrivel while high humidity promotes mold. Pack fruit one layer deep in cardboard boxes in a room out of direct sun. Another option is wrapping individual fruit in sheets of newspaper or waxed paper if you have problems with shriveling.

Some gardeners have success with hanging whole plants upside down in a shed or basement to let fruits ripen gradually. In our dry climate, fruit handled this way tends to shrivel from low humidity.

Monitor fruit condition every few days. Remove fruit that has started to spoil before rots move to adjacent fruit. Ethylene gas produced by ripening tomatoes is a ripening hormone. Remove ripe fruit from the immature ones to slow ripening. Allow ripe fruit to remain to speed ripening of the rest of your tomato harvest.

Green fruit will ripen in about two weeks at 65 to 70 degrees F and about 3 weeks at 55 degrees. Storage below 50 degrees F will result in fruit with a bland, off-flavor. Never store tomatoes in the refrigerator if you want full flavor.

Photo credit: Range of tomato maturities on vine and Harvested tomatoes in box - Carl Wilson

Tomato bacterial spot

2009-09-09T11:26:00.006-06:00

Tomato fruit in home gardens and commercial fields in Denver and the northern Front Range have developed a black spot disease unusual for our area. Dark specks from earlier in the season become raised and scab-like as they enlarge. Sunken centers on older spots are common (see photo left). Spots are brown turning black and can appear blistered. The round spots can merge causing irregular-shaped patterns (photo on yellow tomato below).

Bacterial spot is caused by a Xanthomonas campestris pv. vesicatoria (X.c.v.) bacteria. It is something we seldom see in our area due to our dry climate suppressing most bacterial diseases. This year, the wet early summer and higher humidity favored it. If people overhead instead of ground irrigated they tended to help the disease. The widespread hail and heavy, wind-driven rains that inflicted injuries on plants helped disease spread via wound entry.

At this point there is no way to make the existing spots go away. Early in the season, avoiding overhead watering would have helped. Clean plant debris from gardens and fields this fall. Don’t save seed as it can survive that way. Rotate tomatoes and peppers (another host) to soil growing non-tomato family plants (disease survives in soil for up to 1 year). Eliminate weeds in the tomato/potato family.

Other measures to spray transplants after setting out probably apply to humid climates as we may see little or none of this next year if it is drier and overhead watering is avoided.

This outbreak is a good example of an environmental trigger (rain and humidity) setting off a disease rarely seen even though the host plant and likely the bacteria were present in past years.

Note that the fruit is edible although many people may prefer to remove the skin with the surface spot.

Photo credits: Sunken spots red tomato – Carl Wilson,
Merged spots yellow tomato – Robert Cox

Powdery mildew on vegetables

2009-09-02T18:46:00.010-06:00

The telltale talcum powder look of powdery mildew infections is common on squash and pumpkin vines now. This disease can cause yellow leaf patches on some plants, and distorted buds, stems and leaves on others. Leaves may drop prematurely and flower buds fail to open.

Powdery mildew damages plants by decreasing photosynthesis and removing nutrients from the host plant. Infections weaken plants and leave them vulnerable to other pests. Mildews are host specific and the ones seen on the vine crops will not affect onions or fruit trees.

It is generally thought that plants in areas with poor air circulation are prone to infection. Mildews are different than many other plant diseases and don’t require wet leaves for infection. Warmth and adequate humidity are sufficient. Dense plantings hold humidity on calm days and are often enough to set off disease development..

Do plant vegetables in full sun as shade contributes to weaker plants and also longer moisture retention. Prune or thin plants to increase light and air circulation. Direct water on the soil and don’t wet plant leaves. Avoid excessive fertilizer that promotes succulent leaf tissue that is more easily penetrated by disease organisms. Look for powdery mildew resistant varieties if available.

Most fungicides are preventives meant to be applied before disease appears or at least in the early stages. Examples are sulfur and potassium bicarbonate (sold as Remedy). Read label directions before application. With sulfur, be mindful that it can damage some melon and squash varieties. Do not apply sulfur when temperatures are at of above 90 degrees F or plant injury can result. In the photo right an eradicant stopped the disease and weather conditions were unfavorable for development so new growth is unaffected.

A few fungicides can kill existing mildew infections (eradicants) but are still best applied at the earliest sign of disease. The natural Neem plant-based fungicides (Greenlight Powdery Mildew Killer) and horticultural oils are eradicants. Don’t apply oil to drought-stressed plants or within two weeks of a sulfur spray application. Don’t spray oils at temperatures at or above 90 degrees F.

Thanks to Mary Small for information used in this post

Photo credit 4 powdery mildew photos, Carl Wilson

Winter squash and pumpkin fun

2009-08-27T19:12:00.020-06:00

As summer moves into fall, peek in your neighbor’s gardens and see what type of winter squash and pumpkins they’re growing. They are often standouts for their color and size. I ran into this pumpkin and Turks turban squash arbor (photo) that looked like a space saver. Grow vines vertical rather than horizontal! The centuries old, flat, French “Cinderella” pumpkins (Rouge vif d'Etampes) are also fun (see photo). Now is probably the time to remove any new fruit set on winter squash and pumpkins so existing fruit can mature.

These vines need lots of space to have the many leaves needed to produce enough energy to grow these large fruit and generally require 90 to 120 days to grow. The gardener in this photo is fighting to keep her window wells from being covered by a pumpkin vine. Certain winter squash do come in bush or semi-bush varieties (acorn, butternut, delicata). Vine tips can be pinched to keep vines in bounds but will limit production and quality. It’s better to find a spot with room such as this streetside gardener (photo).

Winter squash differs from summer squash in that it is generally harvested and eaten in the mature fruit stage. Vegetable spaghetti (photo) is probably an exception often being harvested in a semi-mature stage (harvest when the skin turns from green to buff). Pick most winter squash when the skin has hardened into a tough rind not easily dented with light fingernail pressure. The seeds within should have matured unlike the young tender seeds in summer squash. When ripened to maturity, fruits of most varieties can be stored for use throughout the winter.

Winter squash are harvested in September or October, before heavy frosts. Carefully cut squash from the vines, leaving two inches of the often-woody stem attached if possible. Avoid cuts and bruises to the fruit when handling. Fruits that aren’t fully mature, are injured, have had their stems knocked off, or have been subjected to heavy frost won’t keep. Use as soon as possible or compost (watch for seedlings in the compost).

Squash are best stored dry at a temperature between 50 and 55°F. Don’t pile squash more than two fruits deep. Single layers that don’t touch prevent rots from spreading through fruit.

Don’t forget that squash and pumpkin seeds can be dried in a dehydrator or roasted for a healthy snack. When scooping out seeds to use the fruit, wash clinging fibers from the seed and dry or roast.

Photo credits: Squash arbor, Turks turban squash, Cinderella pumpkin, Pumpkin vines over window well, streetside pumpkin garden, vegetable spaghetti squash – Carl Wilson

Hail update and Early blight time

2009-08-19T15:06:00.015-06:00

After the hail -
In my previous post about the July 20 hailstorm that hit the west Denver Metro area, I promised to report back to you. Here is the one month update.

Squash came back fantastically. The crooknecks sent two branches to either side and grew abundant new leaves (photo left). They also have been producing well (photo right). Compare to the photo published in the July 23 post. If the growing points aren’t completely destroyed, it’s obvious squash has a notable ability to bounce back.

The tomatoes are also on the rebound and maturing fruit especially the ‘Sweet Tangerine’ (see photo left). These annual vegetables have amazing resilience to plant-damaging hail events. Patience and water soluble fertilizer applications as discussed in the July 23 post can salvage a partially destroyed garden.

Early blight time -
Late summer is early blight disease time in the tomato plot. Infected leaves develop ½ inch, irregular brown target-like spots (photo below right - click photo to enlarge). As this fungal disease progresses, spots grow together causing lower leaves to yellow and drop. If severe enough, defoliation leads to fruit sunscald and decreased production. Warm temperatures, abundant rainfall, overhead irrigation, and high humidity promote disease development.

Fungal spores are splashed from overwintering plant debris and infected tomato family weeds such as horsenettle and nightshade. Volunteer tomato plants that sprouted from last years stray fruit left overwinter also can carryover the disease.

Manage the disease by eliminating volunteer tomatoes. Properly fertilize plants with nitrogen. Late season nitrogen deficiencies stress plants, making them more susceptible. Avoid working around tomatoes when leaves are wet. Brushing leaves can bruise them and the water aids spores in germinating and moving into leaf tissue. Irrigate at the base of plants rather than wetting leaves. Apply sulfur dust to protect uninfected foliage against infection. And finally, be sure to clean up garden debris thoroughly this fall.

While early blight can be manageable in late summer gardens and fruit can mature before frost, severe cases can limit production.

Appreciation is extended to Mary Small, Jefferson County CSU Extension Plant Clinician, for disease information.

[Photo credit Carl Wilson: Squash leaf recovery and squash fruiting 1 month after hail, ‘Sweet tangerine’ tomato fruit with white hail nicks visible on plants, early blight target spots and yellow leaves on tomato.]

When to harvest?

2009-08-12T18:36:00.010-06:00

At a community garden recently I was asked when eggplant was ready for harvest. It’s particularly tough to know when to pick vegetables you are growing for the first time and perhaps rarely eat.

Most fruiting and many leafy vegetables are not grown until maturity but are picked when sweet and tender. It’s really a balance between allowing more time to produce greater yield versus the best quality. In my mind, quality and flavor for fresh eating win out unless vegetables are being grown for drying (beans) or preservation.

For fruiting crops such as squash, peppers, eggplant, tomatillo and okra, keep in mind that you generally want to nab fruit before seeds fully form. Once seeds form the plant quits producing and the fruit structure begins to toughen or break down.

Cob and pod vegetables should be harvested before sugars are converted to starch. If corn is allowed to go too long by even a few days, fresh eating quality suffers dramatically. Pods of peas, beans and okra become fibrous and toughen. Asparagus should also be mentioned for developing fibers if not picked early.

The hardest thing for me to see is summer squash and cucumbers left to grow large (yellow straightnecks nearing overmaturity photo above). They should be cut young before seeds fully develop. This also keeps squash and cucumbers coming. Do allow winter (also called fall) squash to develop tough skins and seeds. Maturity also develops the flavor of the flesh. Yields will be reduced but this is the compromise with winter squash.

Unless you like green tomato dishes, tomatoes are best ripened to full color on the vine. Peppers picked green promotes more. When allowed to develop red color and seeds, production of more peppers slows. Eggplants can be harvested when only half their mature size and shiny. Dull skinned fruits often have turned bitter and woody (harvest soon in photo right). Tomatillo husks will change color from green to tan. Greener fruit has more tartness than fruit allowed to develop a yellow color.

Leafy salad greens can be harvested when leaves are small and tender. Once seedstalks begin to form, it’s too late as bitterness and toughness have already set in. While outer leaves of Swiss chard, looseleaf lettuce, spinach and kale can be removed in installments to promote more growth, this only works for so long.

Heading greens such as lettuce should have developed firm heads. Cabbage is best harvested loose in summer. Save development of firm heads for fall and winter cabbages (photo left).

Root vegetables can be harvested small (new potatoes and young beets) or allowed to grow to size. Do not allow to oversize and become woody (carrots, beets and turnips) particularly in summer. In fall these roots will keep longer in cool soil before harvest. Parsnips in fact develop better flavor when harvested after frost and store well in the garden.

Photo credits: squash, eggplant and cabbage - Carl Wilson

Summer vegetable watering

2009-08-05T18:09:00.012-06:00

The question of how much to water or how often to water vegetable gardens is a loaded one. There is no one answer because of variations in soil type, how well the gardener has increased the organic matter through amendment additions, temperature, wind, plant spacing and competition, mulched or not, rooting depth and other factors.

Studies show that gardeners tend to overwater. It’s possible to overwater even with drip systems by letting them run all night instead of an hour or two. The misconception seems to be “it obviously takes a long time to apply enough water because the water drips so slowly.”

Tomatoes, pepper and eggplant have a lower water requirement than many vegetables. Overwatering and underwatering both cause blossom end rot of tomato and pepper fruit. Keep soils medium moist but allow soil to partially dry down between waterings. The most critical time to water is during flowering and fruiting. Blossom drop is sometimes experienced in hot, windy weather, in spite of adequate watering. Avoid the temptation to overwater in these circumstances.

Water stress on corn will delay silking but not tassel development. This causes poor pollination of ears when pollen is shed from tassels before silk appears. The pollination problems from water stress causes poorly filled ears or stunted ear development.

Beans require more frequent irrigation than most other vegetables for optimal production. Beans in the blossom and fruit growth stages use the most water of any vegetable. Depending on temperature and wind, beans may use one-half inch or more of water per day. Blossom drop and reduced bloom indicate that beans have been too dry at some time. Even with adequate soil moisture, hot winds can cause beans to drop their blossoms. Tadpole-shaped beans (plump on one end and skinny at the other) are another symptom of past water stress.

An even-moisture supply throughout growth enhances the flavor of leafy vegetables. Cabbage family crops like broccoli and cauliflower develop strong flavors if allowed to become dry.

Water root crops consistently but note that extra water promotes excess leaf growth at the expense of root development. Excess water applied to root crops following a dry period will cause root cracking. Potatoes become knobby if they become too dry, and may decay in the ground if kept overly wet.

It’s probably obvious that the vegetable garden is no place to try to cut corners with water because moisture lapses decrease the quality of harvested vegetables. Avoid problems by consistent watering. Check soil by inserting a screwdriver or digging with a trowel and checking for a cool, damp feel that indicates moisture. Powdery soil that lacks a cool feel indicates dryness and that it's time to water. Checking the soil also avoids overwatering that decreases quality as well as wasting water.

Photo credits: Peppers, sweet corn, Swiss chard, red beets and carrots - Carl Wilson

Floating row covers and vegetable insects

2009-07-30T11:34:00.015-06:00

A previous post discussed germinating seeds with the fabric dual-marketed as seed germination fabric and floating row covers. The fabric covers placed over the top of plants can serve several useful functions including shading plants when transplanting, and shading to extend the life of cool season vegetables as hot weather approaches. They are also used to capture heat for fall frost protection.

Row covers are easy to use. Throw loosely over plants allowing slack for future plant growth. You can also use covers over hoops or wire tunnels such as in the photo above right. Anchor to the soil with U-pins bent from wire and punched through the fabric that touches the ground. Soil also can be mounded over fabric edges to hold it down. Covers allow light and water through and stop movement of insects.

Looking at what insects are trapped under covers with vegetable plants and which are barred access is worthwhile. Row covers can stop plant damage from troublesome insects such as spinach leafminer, aphids, leafhoppers, cabbageworm and cabbage looper. Summer pest protection is offered against squash bug, cucumber beetle, bean beetle, corn earworm, whitefly and grasshopper.

Before declaring victory and thinking covers will solve all vegetable insect problems, remember that several insects spend part of their lives in the garden soil. When they emerge to find their favorite plant food enclosed in a cover that protects them from predator insects, they readily multiply. Examples are cutworms and slugs that lurk in scattered soil locations.

Some insects concentrate on the soil immediately around their host plant and can be thwarted by crop rotation. These include onion and seedcorn maggot, flea beetle, Colorado potato beetle, corn rootworm (left photo larva in soil and right adult on corn silks) and tomato hornworm. Planting in the same location and using floating row covers can set up insect problems with these plants.

If a pest does multiply under a row cover, it may be best to remove it to allow natural enemies such as lacewings and ladybird beetles access to the pests. Also remember that squash and other vegetables depend on insect pollination so be sure not to screen out bees during flowering.

Photo credits:
* Row cover over growing tunnel, David Whiting
* Larva of the western corn rootworm, Frank Peairs, Colorado State University, Bugwood.org
* Western corn rootworm adult on corn silks, Tom Hlavaty, USDA Agricultural Research Service, Bugwood.org

Coping with hail damage

2009-07-23T09:58:00.010-06:00

The hail storms that pounded the west Denver Metro area and Englewood early this week and later the Castle Rock area have prompted this post. Some landscapes took golf ball sized stones. My own garden received a 15 minute dose of marble sized hail leaving only the skeletons of tomatoes (click photo left to enlarge white hail stones and plant destruction details).

First, hail is generally accompanied by an ample amount of rain so stay out of the garden. Wet soil compacts easily and tramping on wet ground only worsens garden problems.
Another reason to stay out of the garden is that plants are more resilient than you may think. Don’t let the damage discourage you.

Most vegetables are annuals and respond to hail pruning with new growth. The limiting factor is the amount of growing season left to them before frost. Brittle plants such as peppers and large-leafed plants like squash (photo right) suffer the most. Leafy vegetables will re-grow and yield, root vegetables are protected underground and survive, and fruiting vegetables generally suffer the most.

Tomatoes tend to surprise in their ability to come back. My hope is that by hedging my bets through planting some shorter season Early Girl and cherry tomato types, I will still realize something where longer season heirloom types will probably not produce. The deep, extensive tomato root systems in my raised beds will help plants recover. I’ll keep you posted on this hope.

Once the water dries and its time to water again, I’ll begin using a weak fertilizer containing nitrate-type nitrogen in the water. Nitrate nitrogen signals plants to grow.

I will also continue sowing mid-summer vegetables for fall harvest as discussed in the July 2nd post. It’s not too late. Though I’m by nature accepting of hail events as a given in Colorado gardening, the act of planting does help soothe a gardener’s psyche. Doing something productive and once again seeing the wonder of germinating seeds is always energizing. Chins up intrepid Colorado gardeners!

Photo credit: Hail damaged tomatoes and Hail damaged crookneck squash, Carl Wilson

The Challenges of Summer Sowing

2009-07-15T19:28:00.015-06:00

Mid-summer sowing of vegetable seed can be a challenge due to weed competition and warm soil temperature.

Weeds germinate quickly in summer and it can be difficult to tell the difference between weed seedlings and vegetable seedlings. One tip is to clear the soil surface of weed seeds by germinating and eliminating them. A week or more prior to sowing, water soil to germinate summer annual weeds such as purslane (see photo below left) and crabgrass and foxtail (photo below right).

Next use a sharp scuffle hoe to cut off the weeds from their roots, disturbing the soil as little as possible. Deep penetration of the soil will bring up additional weed seeds to germinate. Once the soil surface is cleared of weed plants, sow small seeded vegetables at the recommended shallow depth. Use germination fabric over them during germination (see March 6 post for how).

Warm soil temperatures can be a concern for germinating some seeds. The maximum soil temperature for germinating lettuce and spinach is 70 degrees F. The optimum temperature for germinating peas is 70 and many other vegetables 80 degrees F. Seeds become dormant at high temperatures.

Tips for avoiding warm temperature dormancy are to water soil before sowing and sow in the late afternoon so germination will begin overnight when soils are cooler. Shading the soil with seed germination fabric also helps.

Another tip is to pre-germinate seeds. The pea seeds (photo left) were soaked overnight indoors at room temperature (70 degrees F) in a moistened paper towel enclosed in a plastic bag. Do not soak longer or delicate seedling parts will be damaged in planting.

Pre-germinating small seedlings is more difficult. Solve this through fluid seeding. Germinate small seeds on a moistened paper towel in a closed plastic container kept indoors at 70 degrees F. Don’t allow seeds to germinate for more than a few days, only until they just break out of their seed coat. Wash germinating seed off the towel into a sieve with a gentle stream of room temperature water.

Gently stir germinated seeds into pre-prepared fluid seeding gel. The gel is made by dissolving 2 to 3 tablespoons of cornstarch in boiling water and cooling to room temperature. Add the gel-seed mixture to a plastic bag, seal, snip off one corner and gently squeeze the gel onto moistened soil. Cover as recommended and use seed germination fabric to shade. Keep fabric in place until green seedlings are readily apparent. Remove fabric and water carefully until seedlings are growing vigorously.

Crabgrass, purslane and soaked pea seed photos credit – Carl Wilson

The Mean Season is Here

2009-07-08T18:19:00.013-06:00

The arrival of ninety degree F temperatures this week is tough on Front Range gardeners used to a cool spring but even tougher on plants. Plants can’t get up and go inside for a cool drink when things heat up!

Plants that grew up in a cool environment aren’t tough enough to take hot, dry conditions. Their cells and structure are simply wimpy. Expect to see some heat stress, leaf scorch, blossom drop and bolting in the garden.

To help plants transition to the heat, water with care. Vegetables like most plants need some soil drying between waterings but don’t let soils dry completely. This is especially critical until leaf tissue toughens. Some vegetables (tomatoes) benefit from more soil drying than others (onions and carrots). Bean blossoms (photo right) drop when short on moisture and pods fail to fill; they require the most moisture of any vegetable.

One note on America’s most popular garden vegetable, the tomato. Fluctuations in water supply, either excessively wet or dry will cause blossom end rot. This could have been triggered in June downpours or by July heat. It begins as a light tan, water-soaked spot on the blossom end of the fruit (photo left). These spots turn brown to black and leathery and there is no correcting it once the damage is done. Future blossoms that set fruit when moisture conditions are better won't be affected by damage to previous fruit. To manage this condition, fertilize and water properly. Use mulch to reduce moisture fluctuations.

Want more specific watering tips? Check Colorado State University Extension's Water Conservation in the Vegetable Garden garden note.

Bean blossom photo credit, Carl Wilson
Blossom end rot photo credit, Colorado State University Extension

It’s time to seed fall vegetables

2009-07-02T18:17:00.004-06:00

Although it may seem that vegetable gardens have just begun growing well and planting is done, it’s time to seed crops for fall harvest. Sixty day crops planted in July will mature in September as weather is cooling.

Look at seed packets and note the days to harvest. Count back from the first fall frost date, October 11 for the Denver area. With cool season vegetables note that many tolerate the first light frosts of fall very well and an extended harvest period can be expected. Warm season vegetables must be planted to mature well before frost when temperatures remain warm.

Here are some vegetable planting suggestions listed with their typical days to harvest. Cool season vegetables such as peas (65), cabbage (85), collards (55), broccoli (65), kale (60), spinach (40), lettuce (60) and endive (45) are good candidates. Root vegetables such as beets (60), carrots (70) and turnips (50) can be planted this month. Even some fruiting vegetables such as bush beans (60) and cucumbers (55) can still be planted if done by mid-July. The very short season radish (30) can be planted into August with success.

Note that peas planted for fall harvest (photo above) are prone to powdery mildew. Choose powdery mildew resistant varieties. Be sure to provide support such as netting stapled on posts (right) for them to climb to insure good air circulation. Often harvests are reduced as compared to spring plantings. I’m willing to gamble on these Oregon Sugar Pod II’s because I like snowpeas and have a separate area where the air movement is not blocked by tomatoes or other vegetables.

Planting fall crops in “succession” where other spring crops have been harvested is a way to extend harvests past the first frosts and maximize yields from your garden.

Photo credit planted pea seeds and pea netting - Carl Wilson

Got mulch?

2009-06-25T13:44:00.013-06:00

With the arrival of temperatures in the eighties and nineties F along the Front Range, it’s time to mulch the vegetable garden. Soil temperatures are now thoroughly warm and mulches will not prevent the soil warming sought in spring.

The use of mulches now has several benefits. It will blunt the force of hard summer rains minimizing crusting and soil compaction. Mulch slows evaporation and can reduce irrigation needed by 25 to 50 percent. Stabilizing soil moisture to avoid wide swings from wet to dry promotes better quality vegetables and encourages the activity of beneficial soil organisms. Mulches applied now tend to keep soil temperatures cooler during summer and suppress weed seed germination.

Weed and seed-free straw (left) and grass clippings make some of the best mulches. Wood mulches are not recommended around vegetable plants, only for paths in the garden. Collect grass clippings from lawns that have not been treated with herbicides (“weed killers”) for at least a month.

Apply a thin layer of grass clippings (right) which will dry in five to seven days (below), then add the next layer. Two to three layers is generally enough to suppress weeds. Do not add thick layers which will mat, smell and limit water and air movement into the soil. Carefully apply around leafy vegetables as grass clippings are difficult to wash from the leaves and heads of greens.

Both straw and grass clippings can be tilled under in the fall and easily break down to enrich the soil. If straw isn’t desired for tilling under due to appearance, it can be raked off and placed in the compost bin.

Straw and grass clipping mulch photo credit: Carl Wilson

Flowers and fruit set of cucumbers and squash

2009-06-18T18:56:00.013-06:00

It's time or nearly so when the vine crops will produce their first flowers only to have them drop off. What’s going on?

Cucumbers, squash, gourds and pumpkins produce separate male and female flowers on the same plant. The male flowers on cucumbers (right) appear about 10 days before female flowers and outnumber female flowers 10 to 1. Squash, gourds and pumpkins bear 4 to 10 male flowers for every female flower.

Learn to differentiate male from female flowers, be patient until the female flowers appear, and watch to see if bees are present to move pollen between flowers.

Male flowers are attached by a straight slender stem. The stem of female flowers bears a bulge, the ovary, which grows into the future fruit if pollinated and fertilized. In the squash photo above, the two male flowers (left and center) have just faded for the day and are clearly borne on slender stems. The female (still green) flower on the right will open tomorrow and has the swollen stem bearing the ovary.

Male flowers produce nectar and pollen and female flowers nectar only and in greater quantity than male flowers. Bees gather pollen in early morning and switch to nectar later. Flowers open early in the morning and close by noon or shortly after the same day never to reopen.

Note that the flowers of many other plants produce more nectar and are more attractive to bees than the vine crops. While both honeybees and bumblebees can pollinate vine crops, they can easily get distracted by other flower nectar and fail to pollinate your cucumber or squash flowers. If fruit set is poor you can remove male blossoms, tear the petals off to expose the pollen on the anthers, and hand pollinate.

Cucumber and squash flowers photo credit: Carl Wilson

Strawberry time

2009-06-11T18:27:00.002-06:00

June bearing strawberries are coming into their prime (photo right). June bearers fruit over several weeks and ‘Guardian’ and ‘Honeoye’ are good varieties. June bearers are less hardy than ever-bearing types so plant in the warmer cities of the Front Range. You can also mulch crowns in winter after the ground freezes with straw for protection. Like so many other perennial crops, winter watering is useful in dry winters.

Ever-bearers are dependable types for this area and hardier than traditional June bearers. They have two major fruiting cycles with sporadic additional production through the growing season. ‘Fort Laramie’ and ‘Quinalt’ are two commonly available varieties.

Another type to try is the day-neutral berries. They fruit in six-week cycles through the growing season. ‘Tribute’ and ‘Tristar’ are recommended varieties.

Strawberries perform best when planted away from wind in full sun of 8 hours duration. They are sensitive to crown rots so plant in well drained soil with crowns just above the soil. A raised bed with or without hard sides is an excellent growing situation.

I now see many strawberry patches bearing fruit and rewarding gardeners in Denver.

Photo credit – Strawberry fruit on June 10, Carl Wilson

Prepare for succession planting

2009-06-04T17:09:00.015-06:00

Buy your seeds now to prepare for second plantings following harvest of lettuce, spinach, peas, kale and other spring crops. Bolting (seed stock formation) of cool season spring crops is a common sight following the first hot temperatures. See lettuce bolting photo left and spinach bolting photo right below. These plants should be cleared to make room for other vegetables to maximize garden productivity.

Planting of warm season vegetable transplants of tomatoes and peppers and seeds of squash , corn and beans may replace some of these spring crops now that soil temperatures have thoroughly warmed.

Do remember the mid-summer planting opportunity for fall crops of cool season vegetables. Early to mid-July is the time to seed your fall crop of kale, lettuce, peas and other approximately 60 day cool season vegetables. Even though they will be germinating and starting growth under high summer temperatures, they will be maturing in September when temperatures are cooling. Quality can be good as a result. Note that there is also a fall opportunity to plant leafy vegetables desired for early spring crops. See the Colorado State University Extension Garden Notes #719, Vegetable Garden Hints.

Shop for seeds now to have them on hand before seed supplies run out and seed racks disappear until next year.

Lettuce and spinach bolting photos credit, Carl Wilson

Planting, flea beetles and children

2009-05-29T12:30:00.016-06:00

Late May is a busy time in Front Range vegetable gardens. With Memorial Day weekend rains (3 inches in my Denver garden), weeds are growing but easy to pull. Soil is moist for transplanting tomatoes and other warm season plants into the garden. It is also the time to direct-seed warm soil requiring plants like squash, beans, corn and cucumbers.

A visit to the West Washington Park community garden reminded me of several things. The first was how much the heat island effect of city centers has on advancing the season. Their gardens are about a week ahead of gardens in the outer parts of Denver due to the warmer temperature.

Second, early season insect pests are becoming active, foremost among them flea beetle. Germinated beans were already showing holes (photo above left) and upon closer examination, the shiny hopping beetles were present (palestriped flea beetle photo below).

Not only beans but tomato family and cabbage family plants are attacked among other vegetables. Watch young seedlings closely and take action before damage becomes too extensive. While mature plants can withstand some 10 to 20 percent loss of leaf tissue with no adverse affect, seedlings are another matter.

Trap crops such as radish are one good idea. Diatomaceous earth is an effective repellent, and several insecticides including the bio-derived spinosad are effective. Weekly reapplications are often necessary as new plant growth will be unprotected and insects are very mobile. For more photos and control recommendations, see the Colorado State University Extension Flea Beetles fact sheet.

The third reminder I received from my visit is to involve children in your vegetable gardening efforts. Now that school is out, choose age-appropriate garden activities for children and youth, whether they are yours or your neighbors. They will be the richer for early involvement in the garden and receiving the benefit of your presence in their lives.

Photo credits:
Flea beetle damage on bean seedlings, Carl Wilson
Palestriped flea beetle close up, Frank Peairs, Colorado State University, Bugwood.org
Children’s toys among beet seedlings, Carl Wilson

Raspberry pruning

2009-05-22T17:26:00.000-06:00

Red raspberries are very hardy and grow well along the Front Range. Black and purple raspberries do better in milder climates like the fruit producing areas on the West Slope.

While raspberry clumps are perennial, individual raspberry canes should be removed after they have fruited once. In practice, this means that canes should be pruned out after either their first or second year. The trick is to know which year to prune.

The raspberries you have may be either summer (June) fruiting varieties, or fall bearing plants that produce a late summer/fall crop. Summer bearers flower and bear fruit on canes that grew the previous year. Once they fruit, those canes won’t produce a crop again and should be removed. Recommended summer bearing varieties are Latham, Boyne, Laura and Honey Queen.

Fall varieties bear fruit on new growth produced in the summer. Those canes will produce a light early summer crop the next summer. After that, the canes should be removed. Fall bearing canes can be cut down to the ground in early spring if an early crop of fruit isn’t wanted. Fall bearing varieties include Heritage, September Red, Fall Red, Red Wing, Amity, Pathfinder, Trailblazer, Plainsman, Perrone’s Red, Caroline, Autumn Bliss, Goldie and Anna.

Tomatoes love night heat

2009-05-14T16:20:00.001-06:00

Last post discussed heirloom and modern tomato varieties and adaptation. Warmer gardening situations, particularly at night, will help both be productive.

Grow tomatoes in full sun or choose a hot south or west exposure. If there is masonry nearby that can absorb heat by day and radiate it at night, it’s often for the better in our high elevation climate. Examples of these heat sinks are walls [left photo with lattice], pavement and rock.

Some gardeners have placed large rocks between tomato plants to act as “warming stones” [photo right] at night. The nice thing about this idea is that they can be removed if necessary during 90 to 100 degree F mid-summer heat when nights are warm and re-introduced in late summer as weather cools.

People who succeed with longer days to harvest varieties usually garden in the center of a city (heat island), locate their garden in a warm exposure and have heat-retaining pavement or walls near their tomatoes. A warmer than average microclimate at night is the reason behind their success at 5280’, mile-high Denver elevation.

Gardeners in Castle Rock (6200’ elevation) and Colorado Springs (6000 – 7200’) will have shorter growing seasons and more difficulty growing long season tomatoes. Carefully selected exposure, microclimate and use of season extenders such as Wall O’Water®, Season Starter™ and Kozy Coat™ [See May 3rd post] are even more important in these situations. Higher elevation foothill gardeners are more challenged. Mountain gardeners with very short growing seasons should consider growing warm season vegetables in greenhouses.

Have a favorite location or microclimate for your tomatoes? Discuss it by clicking comment below to let us know.

[Tomatoes on brick wall and warming rock photos – Carl Wilson]

Tomato variety choices

2009-05-10T15:16:00.015-06:00

There are hundreds of tomato varieties and your garden center probably stocks ten to twenty. Which one is right for you?

In recent years, heirloom tomatoes have been in vogue. Unfortunately some of these varieties require a relatively large number of days to harvest. Examples are Purple Cherokee (85), Yellow Brandywine (90) ["potato leafed" variety photo below left] and Beefstake (85 days).

In Denver the average growing season is 155 days (May 10 to Oct 11). In some years like 2007 the growing season is short, only 123 days (June 8 to October 8). In addition, there were only 81 days with night temperatures greater than 55 degrees F. Why is this last tidbit important?

Tomatoes require warm night temperatures for growth. Night temperatures below 55 degrees F tend to slow and shut down growth. Depending how cold the nights, growth may take days to resume. This loses you valuable time in the race to tally growing days for maturity.

The high and dry environment of Colorado’s Front Range creates a summer climate that has warm days (80 or 90 degrees F) and thirty degree cooler nights due to radiational cooling (50 or 60 degrees F). Summers are very comfortable for people but not as conducive to growing heat-loving crops like tomatoes that prefer the warm nights of the Midwest and Eastern U.S. where the humidity prevents heat loss at night.

The other factor that decreases yield of tomato fruit is the arrangement of the flower. Varieties that do well here tend to have reproductive parts tucked well into the staminate cone in the middle of the flower. When reproductive parts protrude to or beyond the cone opening, they dry in our low humidity and wither before they pollinate. Tomatoes bred in New Jersey, Florida and other places in the East often don’t yield well here for this reason.

Modern tomato varieties tend to require a smaller number of days to harvest. Many cherry types are 50 to 60. ‘Early Girl’ and derivations are in the low 60’s. ‘Celebrity’ is 70. The ‘Boy’ types are in the low 70’s. My advice is to choose a variety requiring 80 or fewer days to harvest.

Next post, microclimate location and tomato success.

Tomato photos credit: Carl Wilson

Season extenders for early birds

2009-05-03T11:04:00.008-06:00

The Front Range’s mid-May average last frost date means it’s still too early to plant warm season vegetables such as tomatoes, eggplant, peppers and squash. Or is it?

Transplanting vegetables instead of direct garden seeding is one way of extending the growing season. You or your greenhouse grower typically start seed indoors 6 to 8 weeks before plants can be transplanted to the garden. Coddling plants inside when outdoor weather is still too cold gains you valuable “days to maturity” necessary for longer season vegetables to achieve the goal of producing fruit.

Another tool is in-garden season extenders. Products include Wall O’Water® (being filled with water right), Season Starter™ and Kozy Coat™. These plastic cones with water channels in the side use sound principles of physics to keep plants warm. The water absorbs heat from our abundant sunshine by day and releases it at night. Regulate the temperature in the cone by nudging the top open to ventilate on warm days and closed during cloudy weather and cold nights. Plant as much as a month early in April with these devices.

Remember that the mid-May average last frost date is just an average and can vary a month either direction. The snowy garden photo left was taken in Denver on May 24, 2002. Unless season extenders are used to minimize risk, playing the last frost average too closely can trip-up gardeners. This is why some risk-adverse gardeners don’t plant tomatoes until Memorial Day.

Keep in mind that extending the season is much more than frost protection provided by a sheet thrown over plants. It’s about keeping plants warm at night. Tomatoes in particular are markedly set back by nights cooler than 55 degrees F. They simply stop growing even though they haven’t frozen.

While growth is halted by night temperatures in the high thirties or forties, you lose valuable days and weeks in the quest for the necessary days to maturity in our short growing season. It takes plants days and even a week to resume active growth even when night temperatures warm.

Commercial plastic cones with water channels or home-rigged plastic milk jugs filled with water and circled around plants (photo with bean plant right) are valuable in extending our growing season. If you’re itching to plant early, season extenders are a must.

See the CSU Extension Garden Note on Frost Protection and Extending the Garden Season for more information.

Thinning vegetable seedlings

2009-04-30T07:44:00.000-06:00

Thinning overcrowded seedlings is essential following germination. Seedling competition will set back your crop and delay harvest. Some people prefer to thin partially as a hedge against possible later seedling losses. Whether you thin partially or completely to final spacing, do thin. The following photo log provides tips and tells you how. Note that these photos picture thinning for a wide bed or Block style layout, not a row. Wide bed planting results in a greater harvest for your efforts.

New vegetable garden soils

2009-04-23T11:11:00.009-06:00

So you've dug up soil for a new vegetable garden and are less than pleased. Heavy clays, low organic matter content and mixed top and subsoil layers are typical of urban Front Range soils around homes. What are your options?

Just like a human baby can’t do everything that an adult can do, a new garden soil can’t be expected to grow what a long-time garden with carefully cared for soil can. And don’t think that tossing a handful of fertilizer on these tough-to-garden soils will solve your problems. Poor physical soil conditions are the issue, not fertility.

Foot-long ‘Imperator’ carrots are likely not in your immediate future. Perhaps golf ball like ‘Thumbelina’ carrots are a more achievable objective. Better yet, rather than thinking about carrots that require loose soils for root development, consider fibrous rooted, pioneering crops such as lettuce, spinach and kale.

Another thought is to work on soil building your first year. Apply 2 inches of organic compost in the spring and mix in to the top 4 to 6 inches of soil. Plant a summer cover crop such as buckwheat (photo right), till it under in the fall and immediately plant a winter cover crop such as winter (annual) ryegrass. Let the roots of these crops do the work of penetrating these tough soils. Through their burial, add fresh organic matter to feed beneficial soil microbes and build your soil. Ideas on cover crops for Colorado conditions can be found in the CSU Garden Note #244, Cover Crops and Green Manure Crops.

Raised beds with hard sides (wood) or soft sides (soil beds photo left) are another option. Moving or importing desirable soil to construct these beds increases the depth of useable soil and jump-starts your efforts at building a good garden soil. Note that they too will likely require soil building measures such as compost additions and planting cover crops.

A final thought is to avoid overtilling your soil. Beating it up with a tiller is not the answer to building a good soil. Have a good reason to till (turning under a cover crop or mixing in compost for example) and don’t till frequently. Also till at moderate moisture content – not too dry and not too wet. Care for your garden soil and it will care for you.

How do you manage your garden soil? Comments welcome.

Pear Picks

2009-04-18T09:43:00.004-06:00

Pears are a good fruit choice for the Front Range. They bloom late, usually just before apples. Pears are subject to fireblight disease like apples so look for fireblight resistance. Fruit is borne on two year old or older spurs (short, stout twigs) also like spur-type apples.

In choosing a tree for planting, remember that pears are self-fruitful but bear better when planted with a second pollinator tree. Magness is a variety often used for pollination and it shows good fireblight resistance. Any variety that blooms at the same time will serve as a cross-pollinizer.

Both European pears, Asian pears and their hybrids can be grown. Note that Asiatic pears have a lower chilling requirement than European types. Asian pears generally are also less resistant to fireblight.

European pear suggestions include Bartlett (an early summer pear, left in photo) , d’Anjou (right in photo), Bosc and Lucious. Hybrid pears grown here include Maxine (good fireblight resistance) and Kieffer. Of the Asian types, Shinko shows more fireblight resistance.

As in previous fruit tree adaptation discussions [see “Fruit trees on the Front range” March 12], be forewarned that our erratic climate makes this a difficult fruit growing location and these are only suggestions, not recommendations. Comments on your pear growing successes and failures are welcome.

[Pears in basket photo credit, Carl Wilson]

A Tale of Peaches and Potatoes

2009-04-10T18:29:00.009-06:00

by guest writer Robert Cox, Colorado State University Extension Horticulturist, Arapahoe County

Gardeners may wonder why they cannot order certain peach trees from out-of-state nurseries. The catalog description may say that the peach variety “cannot be shipped to Colorado”.

There are two quarantines on peach tree shipments in the state. One prevents the shipment of white-fleshed or clingstone peach and nectarine trees into Mesa County, Colorado. This is meant to exclude peach mosaic virus disease from Palisade area orchards.

The other quarantine prevents the shipment of peach and related Prunus (cherry and plum) trees into the San Luis Valley. Peaches can be the winter hosts for green peach aphid that carries potato viruses. When peach aphids move to potato plants in the summer, the crop can become severely diseased and decimate yields.

Some out-of-state mail-order nurseries do not attempt to determine county of residence when a Front Range Colorado customer submits an order for a quarantined peach tree. The nursery may instead choose not to send a quarantined tree to any address in Colorado. While frustrating, little can be done but look for another supplier willing to recognize that your address is not in the quarantine area.

If it’s a small consolation, many states have similar quarantines on plants that could introduce diseases or insects to an economically important crop. Both peaches and potatoes are Colorado agricultural success stories and worth millions of dollars in income to the state.

[Peach photo credit, Carl Wilson]

Kewl Kale

2009-03-31T20:20:00.017-06:00

I get excited about kale because it is by far my favorite cooked green. When steamed, it retains more texture than spinach. It can also be chopped raw and used in salads. Kale is a good source of vitamin A and calcium. Mostly, I just like the taste, appearance in the garden and ease of growing.

Grow kale as a cool season vegetable in spring and again for fall, filling in with a warm season succession crop in summer. I planted mine before the end-of-March for seed to reap moisture from Front Range spring snowfalls. Do plant by mid April to squeeze in a crop before weather potentially turns hot in June. Quality decreases in hot weather and leaves can turn stringy. Turn to growing more heat-tolerant collards for summer cabbage family greens.

Kale is a tough, pioneer crop for gardeners planting new ground. The round, pellet-shaped seeds are planted only ¼ inch deep (seedlings photo left). Although not as small as lettuce seed, I cover with seed germination fabric to combat soil drying from strong spring winds and intense Colorado sun (see March 6 post, "Seed germination in Dry Climates").

Plants mature in approximately 2 months but leaves can be harvested at any stage of development. Pluck leaves from the outside, allowing plants to push new leaf replacements from the interior to extend the harvest. The new interior leaves are tender and best for salads. Kale stores exceptionally well in the refrigerator.

This year, my spring crop variety is ‘Lacinato’, also known as ‘Toscano’ or dinosaur kale due to the variety’s dark, puckered leaves (left seed packet above). ‘Red Winter’ also known as ‘Red Russian’ is a rugged-looking heirloom variety good eaten raw in salads (right seed packet above). The most widely grown variety in the U.S. is ‘Vates Dwarf Blue Curled’, a ruffled leaf variety developed in Virginia in 1950 (center seed packet above). For an ornamental but edible touch, plant the red-purple leafed ‘Redbor F1’. Keep in mind that the red color develops better in cool, fall weather than in summer heat so planting mid-summer for a fall crop should be considered.

Kale is relatively pest free but occasionally can develop cabbage aphids.

[Kale seed packets and seedling photo credit, Carl Wilson]