On Jan 18, 2:49*am, Bill wrote:
In article ,





*Jangchub wrote:
On Sat, 17 Jan 2009 13:21:36 -0500, Bill
wrote:

*Got down to - 4 F. here last night. Saw where Fairbanks Alaska was
around - 50 F. .
*Here is a question for you. *How are my plants faring here in the lush
-4 F. with no snow cover Vs. the snow covered Fairbanks plants ?

Is this a trick question?
Victoria

http://gotbodhicitta-wangmo.blogspot.com/
Updated daily when able.

*Plants covered with snow never go below 32 F. *Sort of adds another
dimension to the idea of zones.

Bill

--
Garden in shade zone 5 S Jersey USA- Hide quoted text -

- Show quoted text -

Plants covered with snow never go below 32 F. Sort of adds another
dimension to the idea of zones.

That's not exactly true. While snow IS an excellent insulator, it
provides no guarantee that plants under its cover will not freeze. If
this were true, places like Alaska that receive regular heavy
snowfalls that persist through the winter would be able to grow zone 9
plants (minimum temps 20-30F)!! Doesn't happen!! It depends entirely
on the ambient air temperature as well on what the soil temperature
was before the snow cover arrived. Wind chill also has to be included.
And the benefit that snow provides as an insulator is substantially
diminished if it experiences any type of melt - once ice forms or the
snow compacts, the pore space (open areas in and between the flakes
occupied by air) is reduced dramatically

FWIW, my area experienced uncommonly cold temperatures right before
Christmas (teens and single digits in some locations) and even though
we had a good thick snowfall as well (12-24"), a lot of zone 8 plants
were severely damaged or killed. Had it remained no less than 32F
under the snowcover, these plants would have emerged untouched.

1" of snow has been determined to provide an insulation factor of R1 -
about the same as 1" of wood chips, vermiculite, cardboard or a whole
host of common garden mulches. The same amount of fiberglas insulation
has an R factor of about 2.5. You'd need about double the amount of
snow to achieve the same amount of insulation (there's a little more
math involved but the comparison most commonly used is 10" of snow =
about 6" of insulation). The conversion of that to actual heat loss is
a complicated mathematical formula, but suffice it to say the colder
the air temperature, the lower the temperature will fall under the 10"
snow cover.

But you're thinking in the right direction :-) It is far more
desireable for plants to have below zero temperatures and a nice thick
snow cover (in most cases......snow damage from weight is also a
factor) than it is to have temperatures that hover between freezing
and 0F with NO snow cover.