frost on tomatoes

Edna M Weigel (eweigel@juno.com)
Tue, 19 Oct 1999 16:27:16 -0700

We had a disappointing tomato-growing season this summer. (If I
hadn't over-planted with the idea of selling lots, I wouldn't have had
nearly enough to store for us.) I blame it on our cool summer and fall.
I started measuring the overnight lows early in September and the
temperatures in the tomato patch were routinely getting down into the
40's back then. (The tomatoes were ripening, but slowly). Last year I
was able to calibrate all my min/max thermometers and only one of them
read 2 degrees low. Even so, last year, I had readings as low as 27
degrees with no frost damage on tomato plants.
Yesterday morning, I scraped the frost off the thermometer to
read 23 degrees F. Strawberry leaves beside the thermometer were fringed
with frost, so I'm convinced my thermometer wasn't reading way low.
Less than 5 feet away I had tomatoes partly covered but even the
uncovered portions showed no frost damage. In fact, later in the day I
searched the entire garden and couldn't find ANY frost damage at all.
I'm gardening in a frost pocket (Yes, before my Permaculture
friends ask, I've read and reread what Bill Mollison says on the subject
in the Permaculture Design Manual, but I read it after we purchased the
land! I'm working to mitigate the problem.) Another part of my garden
(uphill) is a little warmer; it was 32 degrees yesterday--also with no
damage yesterday.
This morning, the strawberry patch was 21 degrees and
frost-tender plants throughout the garden showed damage except for those
which were covered. Uphill, it was 30 degrees and (except for one basil
plant a little further uphill) tomatoes and basil up there were frost
killed.

QUESTION: Why can some of my tomatoes withstand down to 21 degrees while
other (the same mix of varieties) succome to 30 degrees? One possibility
is that yesterday's low may have been of much shorter duration than this
morning's. Also the humidity may have had an effect; yesterday, we had
lots of frost but this morning, with its lower readings, there was no
sign of frost anywhere. Any ideas out there? I'm confused.
Best Regards, Edna

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