Season continues for some gardeners

'Azoychka' yellow tomato Oct 13, 2014

If you were lucky you escaped Oct 12 scattered frosts or covered tender plants and will be rewarded with an extended growing season. We've been in a pattern of cold-hot-cold-hot. This is expected to continue with temperatures again predicted to reach 80 degrees F in a couple days. Life in the high altitude, steppe climate of Denver, Colorado is always a roller coaster ride.

Tomatoes remaining on the vine will continue to ripen and zucchini will continue to grow larger. Just like betting when to plant warm season crops in spring, deciding when to shut down the warm season garden in fall is a challenge. I know some gardeners who have already torn out their gardens. How many more frost "escapes" will us late season garden gamblers have?

Zucchinis Oct 13, 2014

Of course tomatoes still on plants showing some color such as the yellow Azoychkas in the photo above may yet ripen on the vine. The ace in the hole is they are good candidates for picking and ripening indoors if a hard freeze is predicted (overnight temperatures expected to fall into the mid to upper twenties F). Green ones that are small probably won't have a chance but the largest can be harvested and used as fried green tomatoes.

'Bulls Blood' beet and 'Red Russian' kale
Oct 13, 2014

Meanwhile mid-summer planted, cool season crops such as the beets and kale in the photo will tolerate early frosts. The flavor of kale only improves once frosts begin in earnest. This is shaping up to be a year for warm season vegetable harvests to extend late into fall and cool season crops rewarding the savvy gardener with fall harvests as they always do.

Photo credits: Azoychka tomato, Zucchini, 'Bulls Blood' beet and 'Red Russian' kale all credit Carl Wilson.

Frost advisory tonight

October 7 is the average date of the first fall freeze in Denver so it should be no surprise that a freeze advisory is issued for tonight, October 2. The earliest fall freeze was September 8 in 1962 and latest November 15 in 1944.

Some of your gardens may have been nipped when it got down to 33 degrees F last month on September 11, particularly those on the northern part of the Front Range (Fort Collins, etc.). Often we have warm temperatures after these episodes as we have had for the rest of September. Indeed, daytime temperatures are predicted to be in the mid 70's by the weekend two days from now and reach the 80's by midweek.

With these short one or two night possibilities of a freeze it is worthwhile to cover frost-tender vegetables such as tomatoes, peppers, squash, etc particularly as we get near the average first fall frost date. Use covers to trap heat stored in the soil around plants as was done in the photo. A sheet of plastic or fabric will serve as long as the material is not too heavy to break down plants.

In the photo, double frost protection was used, probably overkill for this early in the season when it has been warm. A poly frost blanket (thick floating row cover fabric) was thrown over the tomato cages and then plastic placed over top and sealed into the soil to trap heat like an enclosed greenhouse. Clothes pins were used to keep the plastic from flapping in the wind.

Invent your own frost protection cover out of materials you have on hand. Just remember to uncover or at least ventilate the next morning as sun will soon cook plants covered tightly with plastic.

Photo credit: Temporary frost cover over tomato cages - Carl Wilson

It's Cherry time

Mature, rarely pruned cherry tree SW Denver

Yields of cherries look reasonable considering the 28 degree F lows we had on May 11 and 12. (See May 12 post on fruit bud damage). Damage at these temperatures was expected to be about 10 percent. Birds also are always a threat and can strip trees of fruit in a few days unless trees are netted.

Tart cherries are hardier than sweet cherries which often winter kill in addition to flower freezing. Sweet cherries are comparable to peaches in this respect.

Recommended tart cherries are 'Montmorency', 'Meteor' and 'Northstar'. If you want to experiment with sweet cherries, try 'Black Tartarian', 'Kansas Sweet' or 'Stella'. Tart cherries are self-fruitful while sweets need a pollinator.

'Montmorency' is the standard tart pie cherry variety that produces a July crop of bright red, firm textured fruit. It is planted in the new (second season this year) "Le Potager" food garden at Denver Botanic Gardens (see photo).

DBG 'Montmorency' cherry

'Meteor' is a very cold-hardy tree growing 12 to 15 feet tall. It develops heavy foliage that can minimize problems with birds. Fruit ripens mid to late July.

'North Star' is a dwarf tree topping out at 10 feet. It sets generally heavy crops of fruit that turn dark red for July harvest.

Note that bush cherries are very hardy and also possibilities. Nanking cherry produces some of the first flowers of spring, can grow to 6 feet and fruit is harvested in July if birds and squirrels don't find it first. Sand cherry is another bush cherry reaching 4 to 5 feet and produces mild-flavored, deep crimson fruit. Both are self-fruitful.

Photo credit: Both Carl Wilson

Time for mid-summer planting

Vacant mid-summer "real estate"

Although warm season vegetables should be coming along well by now, don't forget about what you want to do with the vacant "real estate" in your garden from previous plantings.

April/May/June harvests of cool season and quick maturing vegetable crops often leave holes in the garden. While there is no problem with leaving ground fallow, do know that if planted before mid-July, a harvest can be gained yet this season. "60 dayers" (vegetables with 60 days to harvest or less) are what to think about planting now. Surprisingly, many cool season vegetables work well. Even though planted in the heat of summer, they will mature in cooler fall weather and be of good quality.

For more specifics on what to do to make a vegetable garden more productive from mid-summer through fall, consider attending my "Follow-on vegetable gardening" class at the Denver Botanic Gardens July 12 (click here for details).

Photo credit: Bare ground from harvest of spring crops - Carl Wilson

Growing vegetables in changeable weather

Tomato growing out of Wall O'Water. These
tomatoes are the same ones that were protected
from the hail discussed in the previous post.

By June 9 you might expect the weather to be consistently warm to support the growth of warm season vegetables. At Denver's mile high elevation it isn't so. Low temperatures last night reached 43 degrees F and tonight's low is predicted to be 49 degrees.

Plants such as tomatoes and peppers are set back by lows under 50 to 55 degrees F and take days to resume growth. Development and harvest of your tomato or pepper crop is delayed from the labeled days to harvest number for the variety. That number is based on favorable growing conditions.

Tomatoes growing in Wall O'Waters with a source of heat (warm water in side channels) fare better. Even though the tops may have grown out of the water walls the heat is enough to moderate a cold night and keep the plant actively growing for a close to on-time harvest.

Climate modification through devices such as Wall O'Waters is important for vegetable gardeners to practice in our changeable Front Range Colorado climate.

Squash seedlings growing in a hill.

On another subject I was recently asked why it is recommended that squash and other vine crops be planted as a group in hills. The answer is soil drainage. In addition to last nights cold, my rain gauge measured 0.8 inch of rainfall yesterday. That's enough to saturate and water-log soil without good drainage. This can lead to stunted growth and root rots particularly in our compact clay soils. Although gardeners may get tired of hearing people recommend the virtues of soil improvement for growing vegetables, it is good advice.

Photo credit: Tomato growing out of Wall O'Water, Squash planted in a hill - both Carl Wilson

Another reason for water walls and row covers

The water tubes keep tomatoes warm through
 the sudden drop in temperature

It's been challenging gardening in Denver, Colorado this May. Early in the month it was 85 degrees F on May 4. Then we had snow and a 28 degree F low on May 11. Back to a 84 degree F high on May 18. Today, May 20, it was a hailstorm (see photos).

Kale and mesclun are cool season vegetables
 but this is too much. Brrr!

Thank goodness for growing in Wall O' Waters that provide the tomato transplants some hail protection. I expect plants to bounce back quickly, much faster than tomatoes growing in the open that are now sticks.

The greens under row cover fabric had a little protection and will regrow after their "trimming". It is definitely time to replace the fabric though.

Some gardeners go to the trouble to erect a frame with shade cloth fabric as a hail screen. In our variable climate, it can be a good idea.

Photo credit: Tomato in Wall O' Water after hail, Kale and Mesclun mix under row cover fabric post hail - both Carl Wilson

Fruit bud damage after the storm

May 12, 2014 snow on cherry fruit buds

Cold damage to plants is often much greater the day following a storm. This is when skies clear and without a cloud blanket to hold heat in, radiational cooling comes into play. At high Front Range Colorado elevations with low humidity, plant cold damage from this type of cooling is common.

At this stage of tree fruit bud development (full bloom to petal fall), we can expect 10 percent bud kill at 28 degrees F and 90 percent bud kill at 25 degrees F. This is with a 30 minute exposure and it doesn't matter if it is apples, cherries or peaches. European plums are somewhat hardier and it will have to go down to 23 degrees F to reach an expected 90 percent fruit bud kill and similarly to 24 degrees F for pears.

Cold damage to developing buds of fruit trees can be minimized by planting near the tops of slopes where cold air drains to lower levels and by avoiding blockages (such as fences) to cold air draining away .

Good yields of tree fruit may only be achieved in 2 or 3 years out of five on Colorado's Front Range. This is looking like it could be one of those off years.

Photo credit: Cherry fruit buds in May 12, 2014 snow - Carl Wilson

Greens weather returns

Winds and unseasonably warm Front Range Colorado weather (85 degrees F on May 4) may have been discouraging to those growing spring greens. If you had them protected and growing under a row cover fabric "dome", you gained several advantages. They were encased in a slightly higher humidity environment, shielded from the worst of the winds and recent heavy raindrops (and in some places hail), and protected from rabbits and other marauders.

Now that we're back to cooler weather (more seasonable 60 to 70 degrees F highs), early planted greens are maturing rapidly. It's time for cut and come again harvesting. Shear 2 inches above the soil line so they will regrow providing another harvest.

Another benefit to growing greens under row covers is that soil doesn't tend to be splashed up on the leaves because rain and irrigation droplets are cushioned and filtered through the spunbonded fabric. Less soil on leaves makes washing them a snap. The tempered row cover environment also enhances quality - so tender!

Meanwhile this upcoming Mother's Day weekend highs in the mid 40's F and lows around freezing with predictions for a rain/snow mix augur poorly for those who have already planted warm season vegetables. If you have tomatoes and peppers snug in water walls, no problem. Cool season vegetables will of course be right at home in this upcoming cold/snowy weather.

Photo credit: Mesclun filling row cover, Cut and come again harvesting of mesclun greens - both Carl Wilson

Week to cover-up

Mesclun growing under row cover fabric

A week of 30 mph winds on Colorado's Front Range with both daytime and nighttime temperatures below seasonal averages presents a great opportunity to talk about plant protection and season extension "cover-ups".

Using floating row cover fabric to grow early spring crops made even more sense this week. With soil covering the edges, this lightweight, spunbonded polyester or polypropylene fabric stays in place even though it flaps in the wind. Indeed it should be loose for plants to grow. The fabric provides just enough tempering to moderate wind and cold temperatures while water and light penetrate for plant growth.

If you haven't tried growing under row covers, do so to realize the benefits including wind protection; earlier and increased harvest; pest protection from insects, rabbits and squirrels; frost protection; water conservation and more (see here). Many local market growers are making extensive use of fabric covers for field production. They work equally well in home gardens. Just be sure to peek under the cover once in a while. Weeds find the tempered environment equally conducive for growth and you don't want to miss peak harvest quality because crops are "out of sight, out of mind".

Wall O' Waters set up to warm soil

Another forward looking cover-up this week is preparation for early planting of warm season vegetables. Use of Wall O' Waters to warm soil for future planting of tomatoes and other warm season crops made sense after last weeks warm weather and before this weeks cool-down. Made in Dillon, Montana, this product has a proven record of enabling home gardeners to plant earlier and protect tomatoes from winds and frost. The water-filled channels in the sides are heated by the sun to warm the soil and then protect the plant inside. The manufacturer recommends setting them up at least a week prior to planting to allow for warming the soil for roots.

Wall O' Waters used with black plastic mulch

Wall O' Waters can be used either alone or in combination with another cover-up, black plastic mulch. Even though clear plastic works better for warming soil, black plastic does a fair job and can be used around water walls to prep a garden soil even more for an early May planting of warm season crops. Yes, our average last frost in Denver is May 5 but cold weather often extends later in the month. Plant protection and season extension make sense in our climate.

Photo credit: Mesclun growing under fabric row cover, Wall O' Waters set up to warm soil, Wall O' Waters used in combination with black plastic mulch - All credit Carl Wilson.

Spring sowing of greens

Germination using straw mulch

Time remains to sow spring salad and greens crops in our March to April spring planting period. The nice thing with these crops is that they can be cut at any stage of growth with cut-and-come again harvesting. This means no waste from late sowings that can be harvested before they fade in June heat.

The seedlings in the photo were germinated under a layer of straw mulch. Straw is a useful organic mulch to use in spring before lawns green up and grass clippings become available.

Want to add some pizzazz to your salads? Red orach also called mountain spinach is worth trying. It's native to Europe and the Balkans. Adding red leaves with their mild spinach-like flavor to an otherwise green salad provides a nice complementary color contrast. Orach can be used for presentation purposes as a bed of red on a serving plate. It also can be cooked as a green in soups but red varieties lose their color.

Red Orach  Atriplex x hortensis

Several varieties are available from the magenta shown to purple and various shades of green. Red orach seed is widely available and easy to grow once soil temperatures reach 50 degrees F. Do not sow where spinach, beet or chard have been or will be grown in crop rotation

The best leaves to pick for salads come from the first 18 inches of plant growth made in 40 to 50 days. Orach is both alkaline soil and drought tolerant. It is slower to bolt than spinach but will bolt in summer.

Orach is an annual growing to 4 feet or taller and will self-sow readily if left to mature so be warned and harvest it young if you don't want it coming up all over your garden in future years. Seedlings from saved or naturally spread seed tend to have a lot of color variation.

Photo credit: Straw mulch for seed germination, Red Orach growing with drip irrigation - Both credit Carl Wilson

America turns to Food Gardening

One in three American households (37%) are growing their own food. This is an increase of 17 percent in the last five years to the highest level in a decade. Some 42 million households raise food according to a new report, "Garden to table: A 5-year look at food growing in America", from the National Gardening Association (NGA).

The satisfaction of harvesting your own food 

Of great note is that the largest increase was among younger, millennial generation households age 18-34 (up 63%) and households with children (up 25%).

Millennials are the fastest growing segment of food gardeners totaling 13 million in 2013, a 63% increase in 5 years. Millennials also nearly doubled their spending on food gardening to $1.2 billion in 2013.

Where people don't have their own land to garden, they are joining community gardens. The five year increase in community gardeners is 200% or 2 million more households.

What has caused this food growing revolution? The great recession of recent years may have caused some to turn to growing their own food; the report indicates that household with incomes under $35,000 participating in food gardening increased by 38% in five years. This doesn't explain the total increase as those households represent only 11 million of the 42 million total food gardening households.

The NGA credits the "Let's Move" and White House Kitchen Garden initiatives and strong national leadership from USDA and HHS to increase awareness of healthy eating and educational efforts towards food gardening. Public-private partnerships also receive credit for building more food gardens in communities.

The survey finds that 76% of food growing households grow vegetables. The rest by deduction grow fruit.

Locally in Colorado's Front Range blogs like this one, increased numbers of classes on food growing, a growing number of CSA's, strong community gardening organizations such as Denver Urban Gardens and more political focus on local food production are paying off.

Why not join the grow your own food movement if you haven't already?

Photo credit: Harvesting cabbage - Carl Wilson

'Niwot' fall bearing black raspberry released

Niwot black raspberry (US PPAF) - Photo by Pete Tallman

There is good news for Front Range small fruit lovers this year. Black raspberries (note we are not talking blackberries, a different crop) have not been recommended for this area before now. Recommendations have been to only grow red and yellow raspberries because of cold hardiness issues with black raspberries.

Longmont amateur plant breeder, Pete Tallman, has released the first fall bearing black raspberry recommended for the Front Range. Niwot has at least zone 5 hardiness and possibly greater.

Why is this a big deal? Now we can grow black raspberries that will fruit on first year canes in the fall. Before now the black raspberries available fruited on second year canes (summer types) and those canes were not hardy enough to reliably survive into the second year here. With Niwot, you can grow and harvest all in one growing season, cut canes to the ground in late winter and repeat.

Niwot was selected to be self-fruitful (no second variety required for pollination) and have good production of large fruit with small seeds. Fruit ripen in late August to September. Unfortunately the plant does have thorns.

There is very limited 2014 availability from Henry Field's Nursery that is selling the plant under the name 'Sweet Repeat'. Plants of Niwot won't be widely available until 2015 from Nourse Farms, Inc.

Spring garden transplants

Front Range gardeners most commonly associate transplants with warm season vegetables such as tomatoes planted the end of May. Transplants are also useful in the spring, cool season garden for many of the same reasons.

The mid-March to mid-May period of cool spring weather is short. Planting out transplants as soon as soil and air temperatures allow enables you to mature crops before weather warms in May. This extends your cool season and maintains quality.

One family of plants best transplanted rather than direct seeded into the spring garden is the Brassicas or cabbage family. If broccoli and cabbage plants are large enough and exposed to several weeks of cold (under 50 degrees), they will produce flower stalks.

It is better to start broccoli and cabbage transplants in warmth indoors and plant them outside in mid-April when sustained periods of cold weather are less likely but temperatures are still "cool". It is a tricky concept to grasp.

Broccoli generally does well for gardeners here and if you have never grown it, the superior flavor far exceeds supermarket purchased heads. Early to mid-March is the time to plant seed to grow a 4 to 5 week old transplant ready for early to mid-April planting in the garden.

The photo shows seed of the Burpee broccoli variety 'Sun King' seeded to grow transplants. It's a 71 day variety new in 2013 that is advertised as having unrivaled heat tolerance, a useful trait in our area where warm days can come early. Did anyone living in Colorado's Front Range try it last year and what were your results?

Cabbage likewise grows well here and can be transplanted in the same manner. Cauliflower is much more sensitive to any cultural factor (temperature changes, moisture fluctuations, fertility, insect attack) and is a challenge to grow. Brussels sprouts are longer season plants best planted mid-summer for fall harvest on the Front Range. The spring cool period generally isn't long enough to grow them before hot weather sets in.

Note that most of the Brassica crops are perhaps easier grown as fall rather than spring crops on the Front Range. However they are worthwhile planting in your spring garden as well as later for fall crops.

Photo credit: Seeded broccoli transplants - Carl Wilson

Time to plant hardiest seeds

The hardiest seeds (lettuce, onions and parsnips) can be planted out now that soil temperatures have reached 35 degrees F on the Front Range. Soil temperatures at the online Ft. Collins soil temperature website have been bouncing around between 36 and 39 degrees F since the beginning of the month. Soil temperatures warm on sunny, 50 to 60 degree days and cool in cloudy/snowy weather.

Parsnip seed is notoriously slow to germinate. It may work well to plant them with radishes to gain double use from the area. Quick maturing radishes can be harvested in 20 to 30 days and parsnips require the whole season (100 to 120 days depending on variety). 'Hollow Crown' is an heirloom variety (heirlooms are open pollinated varieties that have been in cultivation 50 years or longer). Other parsnip varieties are 'Lancer', 'Albion' and 'Javelin'.

Planting now means soil should have been fall prepped. Last season's dead plants should have been carted away or composted and the soil tilled and left rough to further break up during winter freeze-thaw. Any compost should have been added then. Note if you grew a winter cover crop, it will require 30 days after tilling under before you can plant vegetables.

Other spring crops require a 40 degree F soil temperature for seed to germinate. These include spinach, kale, beets, carrots, peas and more. Hold off on planting them for now. Of course if you have a soil thermometer and have reached forty at your Front Range Colorado location, proceed with planting.

Photo credit: Parsnip and Lettuce seed packets - Carl Wilson

Learning from the 2013 Gardening Season

The 2013 gardening season was bookended by a very hard freeze on May 1st (19 degrees F in Denver) and a week of rain starting September 9th that soaked gardens and caused record flooding along the Colorado Front Range and plains. The last spring freeze in Denver was May 5th (our average date) and first fall freeze October 4th (October 7th is average date).

Gardeners who planted cool season crops in mid-March achieved a harvest before the May 1st hard freeze although bolting afterwards was an issue. Eighty degree temperatures arrived the last week of May (85 degrees F on May 26) that prompted decline of cool season crops.

For planting warm season crops forty degree lows continued through the end of May and consistent fifty degree F or above nights didn't arrive until June 9th. One 92 degree F day occurred June 3 and then a record 99 degrees F June 10th and 100 degrees F June 11th. Early planting of very warm season crops such as tomato or peppers was best delayed until June or done with water walls if planted earlier.

Vegetable gardeners who haven't considered temperature moderating devices such as water walls until now may want to rethink their approach. It is generally accepted that temperature swings will be more pronounced with worldwide climate change. Take advantage of mulches and season extending devices if you haven't already to achieve satisfactory harvests.