2014 Gardening Year in Review

Frost apparent on tomato leaves.

The best thing about 2014 was probably the extended growing season with the acknowledgment that many vegetable gardeners had to cope with hail along the way. Even though the first official freeze is recorded as October 3, lows weren't extremely cold on that date nor several times later in the month.

Temperatures dipped only into the low 30's F on Oct 3, 12 and 27 in Denver, well within the ability of frost covers to handle. The weather otherwise was warm enough to keep tomatoes growing late and certainly warm enough for mid-season planted greens and root vegetables to mature nicely.

This all came to an end on November 10 with a low of 13 degrees F followed by subzero F lows the next three nights. These temperatures are way beyond the ability of frost covers to handle and effectively ended the growing season for those using frost protection. True to life in Colorado's high altitude steppe climate, daily highs in the 50's and 60's were recorded the end of the month.

Cherry leaves retained through winter.

The unknown factor about this generally warm late growing season suddenly ended by subzero cold is the possible damage to fruit trees.  The most obvious sign of this now is the retention of leaves on apple, cherry and other fruit (and ornamental) trees. 

The cold obviously interfered with the normal leaf abscission process but less clear is how much damage might have occurred to buds and wood. This won't be fully known until spring when lack of bud break and dead wood will show us the extent of any freeze damage. Lack of gradually cooling weather to promote full development of dormancy can deal a crippling blow to fruit trees exposed to sudden subzero temperatures. Let's hope for the best.

Note for those interested in growing fruit trees, I will be teaching a new fruit tree growing class at Denver Botanic Gardens on March 14. See clickable link to DBG in the 2015 class offerings found in the right column.

Photo credit: Frost on tomato leaves, Leaf retention on cherry - both 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

Colorado’s fickle climate

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.