Re: HYB: seedlings in cold frame

This is a sort of a twist on the theme, but might give some useful insight.
I think cold frames can work anywhere, it's just a relativity question, and
also depends on how you build your cold frame.  Even a makeshift cover can
make a huge difference.  A good sealed cover can even have a heater stuck
in for extra cold nights.

I grow cacti too, lots of them.  Many are kept in a greenhouse through the
winter, but many are not.  Until recently I was located down in the valley
near the Rio Grande in Albuquerque, and it got cold in December and January
(was Zone 6b, I think; got to -12 F once while I was there, -5 many times,
and I'm told it was down to -31 in 1972).  Anyway, I used to through cheap
plastic tarps from the department store (usually 20 ft X 30 ft) over the
"slightly hardy" cacti (many from central Mexico) through December and
January, and pulled the tarps off sometime in February (when ever temps.
started regularly topping 65 F in the day).  I staked the edges of the
tarps down with heavy duty tent stakes and put cinder blocks on top of the
stakes (the wind really blows here, but it usually held them down).
Sometimes I would put half hoops of 3/4 inch PVC pipe under the plastic to
keep it from breaking the plants, but usually the cacti were strong enough
that I just laid the tarps on top of them (probably not so good an idea for
Iris and their labels!).  Here snow is rarely an issue, but a heavy snow
could be a problem.

The tarps were generally dark green, brown, or gray, and did tend to trap
heat in the day.  However, clear 6 mil. plastic worked just fine too.
These were sort of makeshift giant cold frames.  They kept the temperatures
about 15 degrees warmer under the plastic on most nights, and even 10
degrees on windy nights.   Not sure how warm in the day, but not too warm
for the plants.  It pulled all the cacti through the winter just fine.  If
I waited too long to pull the tarp though, the plants would start growing
in February and get nailed by frost when the tarp was pulled.  I don't know
if the heat gain would be as good in a cloudy climate with cooler days, but
I'm sure it would be significant.

I haven't done this in a while (warmer and even windier yard, more
greenhouse space, fewer plants now), but will probably do it again
eventually.

Anyway, it really does work.

Dave

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