Environmental matters

On a garden tour this weekend I saw tomatoes 4 feet tall with fruit already set. The gardener said she got an early start and used water walls that were lifted off the plants a week ago. Quite a bit different than the June 1st planted plants I have that are 15 inches tall and just starting to flower. Temperature modification for an early start makes a big difference.

Speaking of temperature, both of our plants will be affected by tonight's low that is supposed to be in the forties Fahrenheit. It's always hard to believe that we could have temperatures this cool only a day following a 95 degree day that tied a record. Tomatoes will be stunted for a few days because the nighttime temperature is below the desirable nighttime low of 50 degrees F for tomatoes. This stunting increases the days needed to grow fruit to maturity. This is typical in high altitude areas in the summer and makes tomato growing difficult.

On another subject, the effects of the hail discussed last time continue. The leaves of all types of plants are taking on a faded appearance from the hail nicks scarring the leaves. Plants look similar to when they are in need of water. Check soil carefully before resuming irrigation and if wet, don't water. Plants also may have yellowed lower leaves from roots that shut down due to the excessive rain that came with the hail. Adding more water too early will only compound the hail damage.

It can't be stressed enough to dig down and check soil moisture in the root zone before watering anytime but particularly following heavy rains.

Photo credit: Plant four days after hailstorm - Carl Wilson

Hail - Nature's pruning

Widespread hailstorms and rain struck the Front Range Colorado area the evening of June 6 from south Denver to Parker and on south to Colorado Springs. Hail sizes ranged from rice grain to one inch sized and even higher. Copious amounts of rain accompanied the storms. In southwest Denver, my garden received 2 inches of rain and rice grain size hail.

The most important action the day after is to stand outside the garden for a post-event look. Check your raingauge and asses the size of the hailstones; pea-sized hail or less is generally not a big problem for plants. Avoid stepping into gardens because wet soil compacts easily. Turn off automatic irrigation systems. Then go away and wait for soil to dry out.

After a few days to a week, pick up detached branches and leaves. Damage to vegetables often looks worse than it really is. These plants are annuals and respond quickly to pruning. When soil dries and it's time to water again, use a low-strength liquid fertilizer to stimulate new growth. Vegetables that are newly established and reduced to sticks may have to be replaced while transplants are still available. It's also early enough to reseed many vegetables. The plants pictured here will recover nicely without replacement.

Patience and waiting for recovery and new growth are the best actions to take following hail events.

Photo credit:  Hail at base of raspberries with set fruit. Hail damage to summer squash and tomato. All credit Carl Wilson

Switch to warm season crops

It looks like the time to plant warm season vegetables without temperature modifiers (water walls, etc.) is finally here. Starting June 1, the forecast is for nights to consistently attain 50 degrees F and days to be in the 80's and even 90 degrees F. With the warm nights, tomatoes, peppers, eggplant and the rest of the vegetables mentioned last post will now prosper when planted.

This also means the end of cool season vegetables like the lettuce and bolting rapini (broccoli raab) pictured above. It's time for these to go into the compost as they are now most likely bitter or fibrous. Rapini in bloom does make a good bee plant if you want to encourage bees or are keeping bees. In tnat case you can wait until after flowering to pull plants.

Direct seed plants from a different plant family such as squash, beets and carrots or plant warm season transplants in place of the rapini.

Photo credit: Cool season vegetables gone by, Rapini blossoms - both Carl Wilson

When will the cold nights end?

Although this title seems like a song lyric, for the warmest of the warm season vegetables it's true. Tomatoes, peppers, eggplant, winter squash, pumpkins, watermelon and cantaloupe have more requirements to think about than not being able to take frost.

This group of vegetables grows well when daytime temperatures are over 60 degrees AND nights are over 50 degrees F.  It's this night temperature part that's problematic in high altitude climates like the Front Range.  The May 20 low was 38 degrees F and nights are predicted to remain in the forties for at least the next week. It likely will be June until they warm sufficiently for planting outdoors without additional temperature support.

That nighttime temperature support can come from water walls or perhaps a warm microclimate location with lots of stone or masonry to absorb and radiate heat. Otherwise the best approach may be to get on the shuttle - moving transplants out by day and indoors at night. This helps harden off plants for eventual transplanting anyway. Hardening off is toughening them up to lower outdoor humidity, wind and higher light intensities especially UV light not present indoors.

For what seems to be everybodys' favorite vegetable, tomatoes, it may be tempting to plant outdoors in a year like this when the apparent last frost was April 16. Stunted growth and susceptibility to pests such as flea beetle results. Plants can normally outgrow this pest when they are established quickly and get up and growing but are severely set back when stunted by cold nights and eaten by pests.

Waiting to transplant can often result in better growth and a harvest that arrives just as early as plants transplanted before the arrival of warm nights.

Photo Credit: Tomato that was transplanted when night temperatures were warm easily outgrows early flea beetle injury (see pin holes on lower leaves) Carl Wilson

Strawberry planting time

Bare root strawberry planting is generally done in early spring meaning April in our area. Container transplants can be planted now into May and even later.

Strawberries are a productive and rewarding fruit crop for our area. They will come into production in a year or less and can be used as an attractive groundcover as well as in pots. Locate them in an area with full sun protected from wind and amend soil before planting.

One of the most rewarding types of strawberries to grow are Junebearers because berries have the fragrance and intense flavor often missing from store bought fruit. The downside of these types is that if spring frost damages blossoms little or no crop will be produced until the following year. Recommended varieties are Honeyoye, Guardian, Kent, Cabot, Mesabi and Jewel. These are generally grown as matted rows.

Everbearing types produce two main spring and fall crops per season with a few berries in between. They are hardy and reliable. Recommended varieties are Quinault, Ogallala (for clay) and Fort Larimie (best on sandy soil).

Day Neutral types flower and fruit on six week cycles over the summer but generally yield less than other types. They can be grown as annuals and removed as you would annual flowers. They are sensitive to drying out and heat. Varieties include Tristar, Tribute and Fern.

Both Everbearers and Day Neutral types are generally grown in individual "hills" even though they may end up being more on the level. Raised mounds are helpful as strawberries are very subject to root diseases and require good drainage. Remove runners to preserve separate plants.

Why not plant some of each type to hedge your bets and gain some of the advantages of each?

Photo credit: All Carl Wilson

Seed germination photolog

A reader has asked that I reprise photos and comments on germinating small seeds in our dry climate. Between winds, intense sun and sometimes warm temperatures like the past 80 degree F weekend, germinating small seeds can be difficult.

Small seeds such as lettuce, radish, endive, cabbage, broccoli, cauliflower, rappini, mizuna and others are covered with only a thin layer of soil at planting. This leaves them subject to death from rapid surface drying as seed germinates. Solutions are frequent light watering in combination with a seed germinaiton blanket. Here's how to use seed germination blankets.

1. Needed supplies include seed, row cover fabric available at garden centers, U pins bent from wire and a garden trowel or tool to make a fine soil surface on the seedbed.

2. Plant small seed such as lettuce by just barely covering with soil. Burying small seed too deep will prevent germination. Lay down row cover fabric over planted seed.


3. Secure row cover fabric by pushing wire U pins through the fabric and into the soil. Bury sides of fabric with soil for further protection from blowing in winds.

4. Water through the row cover fabric. Fabric slows evaporation from soil surface helping seed germination. It also prevents birds from eating seed.



5. Germinated lettuce seedlings visible through wet row cover fabric. Time to remove the fabric that has served its purpose as a temporary mulch for the seed germination period.

6. Fabric removed, Seed germination success!

7. Proceed to grow a successful crop watering more frequently when seedlings are small and cutting back as plants grow more roots. Good eating!

Photo credit: All photos - Carl Wilson

Rye cover crop thoughts

Winter rye also called cereal rye is growing well in these warm days of spring. There are advantages to turning under now while it's still succulent. There is less nitrogen tie-up than waiting until later when it develops stout stems. Remember to allow at least a month after turning under before planting.

Winter rye (not Italian ryegrass which is different) is one of the hardiest cereals and is also drought tolerant. It can be planted early or late in fall, either by itself or with a legume such as hairy vetch or Austrian winter pea for adding nitrogen.

By itself it will scavenge soil nitrogen from last season and keep it from leaching over the winter. It grows well on sandy soils and is good for preventing wind erosion. Rye produces a lot of biomass adding to soil organic matter.

You can also leave a row of rye to shield early planted vegetables from spring winds. Peas, lettuce and other cold soil tolerant crops can now be seeded as soils should be well over 40 degrees F along most of the Front Range.

Photo credit: Winter rye closeup and in bed - Carl Wilson

New USDA Hardiness Zones Announced

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.