Re:OT:wind chill

From: "Dan & Marilyn Mason" <dmason@rainyriver.lakeheadu.ca>

Jan. 18 Bill Shear wrote:

<I wonder if wind chill is as important to low-growing plants as
it is to humans.  Wind chill temperatures are calculated as their
effect on us. It can be quite different within a foot of the
ground, where wind velocities are much slower.>
----------------

It is my theory that wind chills are dangerous for people because
the cold wind is good at quickly removing heat from the exposed
object. An exposed plant quickly cools to the temperature of the
air, but this is not dangerous to the plant if it is hardy for
that area. Once the plant has cooled to the air temperature the
wind cannot remove more heat from the plant.

But the cold wind is very dry. It is quite capable of removing
moisture from the exposed parts of plants. Prolonged extreme
cold and wind can have a drying effect on plants. This probably
would have more damaging effects to semi-hardy shrubs than
iris. But iris growing in a wind exposed site that did not have
mulch or snow and went into the winter with dry conditions
could be further dried by extended periods of low windchills.

This is just my theory. My iris have always been snow-covered in
the coldest weather. I have lost very few low growing plants from
winter weather thanks to our continuous snowcover in winters. I've
seen more damage on semi-hardy shrubs, blackberries, black
raspberries, grapes, apples, roses, etc. On semi-hardy deciduous
plants the parts not receiving protection from the snow die back
after cold winter weather.

Dan Mason  zone 3, NW Ontario
dmason@rainyriver.lakeheadu.ca

(Where if our kids have appointments 60 miles away this time of
year, it will almost always occur on one of the colder days of the
winter.)


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