Field of Science

Wind chill and plant cold hardiness

A reader asks an interesting question.  How does wind chill affect plants?  If a plant is cold hardy to say 10 F [22 degrees F below freezing for those of you who use rational C units], and the wind chill is -20 degrees, will the additional cold hurt or kill my plant?  OK, the short answer, no. The wind chill doesn't affect plants, only the absolute temperature. The wind chill factor is how much colder the temperature seems to us warm-blooded animals because of the wind, but it is still the same temperature.  Remember the wind chill factor is the number of degrees that is subtracted from the actual temperature; it is often reported so that you don't know if it is the apparent temperature that is -20 degrees or if you must subtract 20 degrees from the actual temperature.  But to the plant it is simply 10 F; not being warm-blooded plants don't get colder because of the wind.  Here's a couple of refreshers on cold hardiness from TPP's archives:
Why don't trees freeze? and It's the extremes. This winter, '14-'15, with the jet stream positioned where it is, our snow is coming from fronts moving up from the south west, and then the cold air pushes back south and a blast of frigid air follows.  So this winter has seen several nights where the temperature has reached 32-39 degrees F below freezing. Zone 5 plants will be fine, but any plant not fully hardy in that zone may get damaged or killed. So TPP has a bad feeling about the Helianthemum replacements. They were under a good snow cover for the first couple of cold blasts, but the last blast caught them bare, naked of snow. Ah, well. What kind of gardener are you if you don't push the envelope a little says the man with an Ashe Magnolia to plant come spring. 


Anonymous said...

How much insulation does 9 feet of snow amount to? (Adios Korean maple I'm afraid.) For me,"pushing the envelope" is trying Zone 4 plants. But calculating the effect of total burial is beyond me. Good luck with your on-the-edge plants.

The Phytophactor said...

Snow is a great insulator for plants, so not sure I'd count the maple out. My southern Mother had a mimosa in far upstate NY planted where the snow always drifted, and the parts under the snow always survived.