Not sure if you all have noticed, but 2011 has already had some really cold nights. So cold that my wife is going to Montana today to get warm.
As plant enthusiasts, horticulturists and plant growers, we all are fully (and sometimes unfortunately) aware of the effect of cold temperatures on our plants in the spring, summer and fall. In 2010, many of us were blessed with a relatively long growing season, with no widespread frosts or freezes after the end of May. We also didnt have a true killing frost until Oct. 21. Thats a whopping 149-day growing season!
Unfortunately, in 2010, additional temperature-related factors affected our gardens success or led to its failure:
b Cool air temperatures equal cool soil temperatures in the spring and early summer. Until your gardens soil dries out and starts to warm up you wont see much plant growth or seed germination.
b June was very dry and hot. If transplants are stressed going in, these conditions didnt help. Nor do wild swings in day and night temperatures (13 days last season had temperature differences greater than 40 degrees).
b Early frosts, such as the one on Sept. 11, may have ended the production from our warm-season crops.
Focusing on our present weather, these cold temperatures this first part of January may have a significant effect on many of our perennial crops and plants. Lows of -11, -26, -20 and -13 degrees, coupled with long periods of frigid cold (on Jan. 1 and 2, the temperature was below zero for 16.5 continual hours), have the potential to kill entire plants, especially those that are borderline hardy for our area. Based off the USDA Hardiness Zone Map, Durango is classified as Zone 5b, which means that our average minimal temperature is between -10 to -15 degrees. Therefore, if you plant a Zone 5 plant, you are running the risk of plant death.
Throughout the San Juan Basin, there have been reports of temperatures as low as -28 to -32 degrees; our local airport reported -26 degrees on New Years Day. Temperatures as low as that run the risk of affecting the survival of Zone 4 plants (-20 to -30 degrees), which I usually feel comfortable recommending.
Similar to summer conditions, there are many variables in winter that can affect the survival rate of your plants:
b Snow coverage when the low temperatures occurred. According to research from Rutgers University, 9 inches of snow on the ground provides a tremendous amount of insulation. When the air temperature registered -14 degrees, the temperature at the soil surface under the snow was 28 degrees.
b Weather conditions when the plants entered dormancy in fall. The cold snap in late November may have helped winterize our landscape, making the effects of the recent cold less damaging.
b The effects of light, wind and microclimate will also greatly affect plant survival.
The focus of my next article will be on how cold temperatures can affect our fruit trees. Oh, and please dont burn those seed catalogs to stay warm spring is only four months away!
firstname.lastname@example.org. co.us or 382-6464. Darrin Parmenter is director and horticulture agent of the La Plata County Extension Office.