Re: Re:OT:wind chill
From: Haggstroms <hagg@alaska.net>
Dan & Marilyn Mason wrote:
> 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 -
Your theory is absolutely correct. Desiccation from winter wind, or
"windburn" is very damaging to any above ground (or above snow line) plant.
Some plants are able to resist this type of winter damage well, and some do
very poorly at it. But, as you state, in a very cold and windy winter, with
little snow cover, even resistant plants experience die back to the snow
line.
What winter winds actually do is accelerate a problem that is already
present in winter air, which is that cold air can hold little moisture - the
colder the air, the less moisture it can hold. A very long cold winter will
by itself desiccate susceptible above ground plant material. The winter
winds exacerbate this problem. It is the same phenomenon as "freeze-drying"
or "freezer burn". Even those in Florida can experience winter burn in
their freezer :-)
So, low temperatures themselves may not be a problem, or a winter wind by
itself. But when you combine the two they certainly compound the problem.
There is an anti-desiccant on the market, designed to reduce transplant
shock for shrubs, trees etc, which I've tried used for new shrubs going
into winter, but the one I saw came in a spray can, and I can't imagine
trying to spray all one's shrubbery and trees every fall to prevent possible
die-back. But the concept is valid.
Kathy Haggstrom
Anchorage, Ak
Zone 3
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