Cold Terminology
James Waddick (Tue, 13 Nov 2007 14:06:50 PST)

Dear Friends,
it seems to me there is a lot of comparison between Apples
and Oranges going on here.

"Frost- the er, white frosty stuff, is a physical result of a
combination of temperature (air and surface) as well as humidity and
barometric pressure (altitude). It is not a specific temperature.

Freeze - is the empirical standard temperature where water
freezes- i.e. 32 F or 0 C.

Cold Damage - can occur in plants depending on a wide variety
of factors unrelated to frost or freeze. Experience from many growers
suggest that there are a few specific temperature thresholds:

50 F. some extremely sensitive tropical plants such as
Sansevieria, some orchids etc show definite signs of damage at
temperatures around here or less. Leaves can show necrotic spots and
discoloration below 50 F.

32 F There obvious damage due to freezing of water crystal
in succulent foliage. Leaves collapse and desiccate.

25 - 27 F - a commonly low temperature for some marginally
hardy plants. Able to be unaffected by freezing temperatures, but
just barely.

15 F or so for another group of slightly hardier plants.

The observant may see some relationship with Hardiness Zones
in 10 degree increments. I think growers with a wide experience in
different climates and keen observation skills will see that some
plants can simply tolerate more or less heat/cold than others.

Just a suggestion. Jim W.

--
Dr. James W. Waddick
8871 NW Brostrom Rd.
Kansas City Missouri 64152-2711
USA
Ph. 816-746-1949
Zone 5 Record low -23F
Summer 100F +