snow cover; was: Re: [pbs] pushing envelopes

Boyce Tankersley
Fri, 16 Jul 2004 13:03:47 PDT
We've had a NWS weather collecting station at the Chicago Botanic Garden since the early 80's. Winter snow cover is a hit or miss event in this area. It does get very much below freezing without snow cover during an 'average' Chicago winter.

Boyce Tankersley
USDA zone 5 on the west side of Lake Michigan

-----Original Message-----
From: []
Sent: Friday, July 16, 2004 12:47 PM
Subject: RE: snow cover; was: Re: [pbs] pushing envelopes

Three years ago I set up an experiment to measure the effect of snow cover,
but unfortunately winter that year was a total non-event, and so I
discovered nothing.  But what I did was this (with the help of a
meteorologist friend): I dug a pit in undisturbed soil and inserted
temperature probes at three depths (don't recall exactly, but probably 12",
6", and 2"), and perched a fourth just above the soil. The pit was then
filled and watered heavily to settle the soil. A pole holding a yardstick
(for measuring snow depth), a hi-lo thermometer (for air temps), and
connectors for the probes was erected at the same site. The idea was to go
out each morning and measure soil temps at all 4 depths, the high and low
temps for the last 24 hours, and the snow depth.  This would all have
worked beautifully, except that nothing of meteorological interest happened
from November through January (when I gave up taking readings) or at any
point thereafter.  The idea was good, however, and I hope to try again this
winter (the last two have been quite interesting winters).

Jim is right to suspect that soil temps tend to stay pretty balmy under a
lot of snow.  After our 5' snowfall this winter, when I dug pits in front
of the greenhouses so I could open the doors (this meant I literally dug a
pit, hopped down into it, and continued digging until the door could be
freed), the soil underneath was not frozen.  I've long suspected that it
rarely freezes more than 2-3" down.  Hence the experiment, which really
should be repeated.

Seneca Hill Perennials
Oswego NY USA
Zone 5

Original Message:
From: Jim McKenney
Date: Fri, 16 Jul 2004 13:23:15 -0400
Subject: snow cover; was: Re: [pbs] pushing envelopes

At 07:06 PM 6/26/2004 -0400, Ellen Hornig wrote:

>We have excellent snow cover, and this is no doubt part of the

I envy Ellen's snow cover. Here, several hundred miles south of Ellen,
where the winters are ostensibly milder, many of the plants she mentions
are not reliable in the open garden. Eucomis, Galtonia, Crocosmia, many
Kniphofia and others simply don't survive bad winters. Snow cover here is
brief and erratic. 

Years ago I had a conversation with a Canadian agriculturist who assured me
that cold as the air might be, down under the snow cover the temperature
was close to 32 degrees F. It's hard to believe, but Ellen's success in an
area with snow cover seems to support this view. 

Jim McKenney
Montgomery County, Maryland, USA, USDA zone 7, where we don't have reliable
snow cover, but we sure do have lots of mulch.

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