Did they frost or did they freeze?

[Nightshade]

After loosing two rounds of fresh plants this spring, i realize I don't have ZDD, I have Microclimate Denial Disorder. The side of the yard where my tomato plants are growing is in some strange alpine zone of its own.

I covered my plants both times and they still froze back. How cold would it have to be for that to happen ....probably at least 30 degrees? Or is something wrong with my plant covering techniques? I used upside down pots and buckets the first time and pillowcases the second.

I didn't know what to do with the first frostkilled batch, so i cut them back to the ground. Some started to grow back almost immediately, and came through the second kill-off in pretty good shape, so maybe some of the latest victims will still make it..



Oh well, at least those plants are going to have great root systems by the time they are big enough to set fruit. And, thanks to the generosity of those of you who started the noob off with seeds last year, I still have some back up plants if i need them.

Jan

[dice]

Are you at the bottom of a hill or something like that? Cold air
flows downhill and will pool in low spots. If your plants are in
one of those low spots, the air around them can be degrees
lower than what a thermometer outside on your porch reads
or what the weather service claims the low temperature in your
area was the night before.

[Nightshade]

You got it Dice. We live at the bottom-most end of a valley that is two miles wide and 7 miles long. Lots of cold air comes rolling down that long hill. Add in the wind chill factor when we have 40 and 50 mile gusts for two days straight and the ordinary light duty frost protectors just can't do the job.

jan

Originally Posted by dice

Are you at the bottom of a hill or something like that? Cold air
flows downhill and will pool in low spots. If your plants are in
one of those low spots, the air around them can be degrees
lower than what a thermometer outside on your porch reads
or what the weather service claims the low temperature in your
area was the night before.

[dice]

Growing in raised beds, tall ones (like 12" or more), or raised
furrows (called "hipped up rows" by farmers), and planting
on a slight slope can help. It raises the plants up above the
lowest point around them, letting the coldest air flow down
the paths between the beds or furrows.

Someone from Texas reported recently that on a cold night his
cukes and so on that were growing at ground level were badly
damaged, while his tomato starts in raised furrows seemed to
have no damage. If it were *really* cold, of course, like a solid
25F, the raised furrows would not save them, they would freeze
anyway, so this helps most in those borderline situations where
the average outside air temperature is right around freezing.

You probably need to adjust your "last frost date" later in the
year by a few weeks to allow for your particular microclimate,
too.

Dealing with the wind is a whole separate issue, and you can
probably imagine the alternatives (park an RV upwind, build
aerodynamic berms around the garden that steer the wind
up and over, super-heavy duty cages anchored with double
T-posts, etc).