Winter Musings

Winter cover crop B.R.
 (before rabbits)

Cover crop A.R.
(after rabbits)

As I look at my winter cover crop planting clipped low by rabbit(s), I’m waxing philosophical about gardening and working with nature. It was planted in late September and is well established with the warm fall and winter to date.

While much of the top growth is lost, I know there is substantial root growth that also will provide organic matter for soil improvement. 

It will grow out again early before I turn it under in spring so I’m not too worried about gaining benefits from this winter rye/Austrian winter pea mixed planting. There is the perfect and then what results once the real world has its say.

Speaking of the real world, I heard lots of complaints about poor tomato yield last season. Me too. While we didn’t have any 100 degree weather, there was enough high eighties and ninety degree weather to cause poor pollination and blossom drop. 

My plants finally achieved blossom set in mid-summer and particularly the small-fruited varieties had time to produce a late-summer crop.

It’s good that every year is different and hope springs eternal with gardeners including me. I already have purchased tomato seed to start this season’s transplants come spring.

 Photo Credit: Both photos Carl Wilson 

Time to mulch warm season veggies

Tomatoes newly mulched
with grass clippings

With the arrival of summer this week but more importantly now thoroughly warm soils, mulching of warm season vegetables is in order for saving water.

Mulching is frowned on earlier because it delays heating of soils to temperatures suitable for warm season vegetable development. Later mulching is especially important for peppers but also tomatoes, eggplant, etc.

Grass clippings from lawns not treated with herbicides and not having a lot of weed seed work well. A one to two inch layer is sufficient. It's better to apply two thin layers a week or more apart rather than a thick layer that starts to rot and smell. Straw, again from fields not treated with herbicides and with low weed seed content, also works well.

Tomatoes grow in full
sun in containers with drip
irrigation on driveway

I'm often asked how to grow tomatoes and other fruiting vegetables at homes where full sun is at a premium. How about in containers on the driveway as this enterprising homeowner did? You can even equip them with drip irrigation for easy watering. Driveways often are free from obstructions blocking sunlight if patios or decks have pergolas or are covered for shade.

Photo credit: Grass mulched tomatoes and Driveway container tomatoes both credit Carl Wilson.

Is setting up Wall O' Water's still worth it?

Newly set up Wall O' Waters

I've written before about the Wall O' Water product for season extension in Colorado's high and dry continental climate. This is the one with tubes in the side of the plastic cone that you fill with water to absorb the sun's heat and keep the plant growing within them warm.

What about setting them up now in late May when the growing season is supposedly on and the danger of a spring freeze low?

My answer is it is still a good idea for tomatoes, peppers, eggplant and warm season vegetables. Why? Now they can be used not so much to extend the season and protect from a spring freeze but to warm plants at night.

Have you noticed that nights are still in the forties F?  As I mentioned in the April 22 post on "Choosing tomato varieties", the minimum nighttime temperature for growing tomatoes is 55 degrees F. In our high elevation climate with low humidity, there isn't anything to hold in heat on clear nights so radiational cooling is extreme.

If you look at historical average low temperatures for Denver, we don't exceed 55 degrees F until June 22nd. Even so, we often have nights over the summer below 55 degrees in June, July and August - 16 nights in 2016!

Go ahead and set up a Wall O' Water when planting your tomatoes out over Memorial Day to take the chill off the night temperatures. Your plants will get up and growing faster for your effort.

Photo Credit: Newly set up Wall O' Water - Carl Wilson

Click here for manufacturer's website Wall O' Water

Determining tomato varieites

The pun in the title is meant to call attention to the growth habit of tomatoes as gardeners pick varieties for planting this month.

Determinate tomato growth ends in a flower while indeterminate types produce vegetative growth and flowers until frost. Of course there are some inbetweens. They are  known as semideterminate types but even that doesn't fully capture growth habits as some are sprawling and some short, upright plants.

Determinate 'Fantastico' F1 hybrid
grape tomato. All-America Selections.

What's the big deal about growth habit other than considering it in allocating garden space, planting distances and staking needs? A lot.

Last time I wrote about the narrow temperature range for pollination of flowers. Determinate types tend to produce flowers all at once and then not many additional ones as they top out. That is great if you want many tomatoes at one time for canning or marketing. It doesn't work out so well if the bulk of flower production occurs during a cold or hot period that is poor for pollination and results in few fruit.

The other consideration is fruit flavor. As Randy Gardner, tomato breeder at the Mountain Horticultural Crops Research station of North Carolina State University, has been noted as saying, the fruit of determinate types will never have the flavor of indeterminate types. They don't produce the ample amount of leaves to photosynthesize and supply fruit that indeterminate types do. He is the breeder of the "mountain" tomato series including 'Mountain Spring' and 'Mountain Merit'. Both are 70-some day to maturity types and are recommended for commercial growers in Colorado.

Mr. Gardner has also said in interviews that his varieties are bred for commercial producers but were adopted by home gardeners in the East when an outbreak of late blight widely took out plants a few years ago. We have little problem with late blight in the dry West, especially if you water at the soil level and keep foliage dry (no overhead sprinklers).

While Mr. Gardner and other plant breeders have bred more disease resistance into their hybrids than heirlooms have, that generally isn't a big reason for choosing varieties here unless you have a problem with TSWV or some other specific disease.

In general I recommend that home gardeners choose indeterminate types or at least a mix of indeterminate and determinate. Even if you want to grow tomatoes for paste you have the choice of indeterminate 'San Marzano' or newer, shorter-season indeterminate hybrids rather than determinate 'Roma'.

Know the growth habit of the variety you are planting as well as the days to maturity (80 days or less in Denver) before purchase.

Photo Credit: 'Fantastico' F1 tomato - All-America Selections

Choosing tomato varieties

The Front Range has varied topography, elevations, location in relation to nearby mountains and microclimates. Every season is different as temperature and rainfall vary through the growing season. A tomato variety that performs well one year may not the next.

For example last season (2016) many people complained that they had few ripe tomatoes by late summer. Summer heat was likely to blame for poor pollination and fruit set. Denver had 44 days from June through August with temperatures over 85 degrees F, temperatures where blossom drop is likely. Greeley had 68 days.

Fortunately we had a fall with extended favorable temperatures so gardeners had time to ripen late-set fruit.

Not only temperatures too high to set flowers but also night temperatures too low are a factor. Our neighbors to the north in Cheyenne had 52 nights in the June to August 2016 period with temperatures under 55 degrees F, poor conditions for pollen viability and pollen tube growth to set flowers. Denver had 16 nights in the same period and Greeley 33.

While it's challenging to choose tomato varieties to grow in our Front Range conditions, the good news is that there are lots of varieties out there and more every year.

My recommendation is for short season varieties (80 days to maturity in Denver, 70 days or less in Cheyenne). Varieties with northern adaptation are also good candidates. These might include Russian heirlooms such as 'Azoycha', 'Aurora', 'Anna', 'Alaska', 'Paul Robeson', 'Black from Tula' or German 'Gardener's Delight' , 'Blondkopfchen' and 'Bloody Butcher'.

Also hybrids such as 'Northern Exposure', 'Juliet', 'Parks Whopper', 'Big Beef', 'Summer Girl' and 'Fourth of July'. New this year is an All America Selection winner 'Midnight Snack', a cherry type that is touted as an advance in flavor for purple types.

Hybrids from crossing heirlooms are also gaining popularity and include 'Brandy Boy,' 'Big Brandy', 'Genuwine' and 'Perfect Flame'.

I also recommend a mix of varieties including both heirlooms and hybrids. Chances are that if one doesn't perform well under this year's weather conditions, another will.

Photo credit: Windowsill tomato starts - 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

Tomatoes love night heat

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

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