Frost Point
Moore wrote:
>
> Jane, your appended note:
>
> >Jane Mattei IL/Z5
> >1996 First frost: 11 Oct 96 (about 4 degress)
> >Happy Thanksgiving, Canada!
> >
>
> Reminds me that I've always wondered what exactly that means --4 degrees of
> frost. Is it 32 minus 4, or 28 degrees? They say it in lots of British
> books, etc., too. Is it the same as in Canada?
>
> --Regina Moore (moores@friend.ly.net)
> Centreville, MD Zone 7
> on the Chesapeake Bay
> Two light frosts here, enough to put spots on the basil, but nothing serious. :)
Regina:
I suppose that is an "english" grammatical construction and is,
therefore, more common in Canada than the US, although I would expect
those "down under" to recognize it as well.
You are quite right about it's meaning though. If freezing point is
32F/0C then four degrees of frost is 28F/-3C. The Farenheit scale is
technically more precise due to finer gradation, which accounts for the
difference. I was also assuming my current context, which is degrees
Farenheit.
I tend to watch more for "degree" of freezing than just whether or not
it has happened. That little nip of frost killed off the tomatoes and
damaged exposed fruit. My roses and other perennials, however, are
completely unaffected by such a little chill. They are not damaged until
there are more than 5 degrees of frost for at least two hours. Raising
the beds by about a foot further encourages cold air to flow off them
and can give me up to two extra weeks in the average year before I see
any significant frost damage. Raised beds also warm faster in the
spring, so the plants get a bit of a head start at the front end too.
I'm sure most people aren't quite this obsessive about monitoring so
closely, but old habits die hard. I attribute my preoccupation to many
years of growing roses in the Great White North. If I wanted them to
survive, I had to learn what to watch for.
BTW heathy SI's can withstand much more severe freezing with little or
no damage as long as they have enough water. Their massive foliage acts
like a big blanket, protecting them and moderating root zone temperature
changes quite nicely. The TB's were always long gone before the SI's
even started to look ragged.
Jane Mattei IL/Z5
jmattei@mail.leoburnett.com
