permaculture

[kris kaul <kriskaul@yahoo.com>]

I'm planning to put a small lean-to polycarbonate greenhouse on the south 
side of my house.  The floor will be insulated underneath (it can't be at 
ground level due to tree roots), and we'll do everything we can for thermal 
mass - water containers in front supporting the beds, and a brick paver 
walkway - but I'm still concerned about how cold-hardy it's going to be here 
in Michigan (it will only have solar heating).  At a minimum, I'd like to be 
able to start seeds in it in March (as opposed to in my living room)...  I 
would love to hear of others' experiences with small greenhouses in cold 
climates, and what diy modifications they might have tried to prevent the 
plants inside from freezing.  I'll be glad to share whatever I learn from my 
experiences.

Keep well,

Kris
Southeast MI Permaculture Guild
http://southeasternmichiganpermaculture.ning.com/




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At 7:26 PM -0800 11/12/09, kris kaul wrote:
>I'm planning to put a small lean-to polycarbonate greenhouse on the
>south side of my house.  The floor will be insulated underneath (it
>can't be at ground level due to tree roots), and we'll do everything
>we can for thermal mass - water containers in front supporting the
>beds, and a brick paver walkway - but I'm still concerned about how
>cold-hardy it's going to be here in Michigan (it will only have
>solar heating).  At a minimum, I'd like to be able to start seeds in
>it in March (as opposed to in my living room)...  I would love to
>hear of others' experiences with small greenhouses in cold climates,
>and what diy modifications they might have tried to prevent the
>plants inside from freezing.  I'll be glad to share whatever I learn
>from my experiences.
>

I have no experience growing in cold-winter climates, but I did grow
all my tomato and pepper seedlings outdoors this year in a primitive
cold frame, inspired by "wintersowing" (there's a website that
explains the idea, which did start in a cold-winter climate, as well
as offers of a few free seeds). IIRC, the temperatures didn't dip too
much below the 40s when I started my seeds. I ended up with about 200
tomato seedlings and a dozen peppers. In your climate, I'd guess that
some kind of "blankets" or heavy row cover would be sufficient to
conserve heat overnight. (Doesn't Eliot Coleman grow year-round in
unheated greenhouses in Maine?)

It got pretty toasty inside my cold frame, so one of the crucial
modifications was allowing some of the hot air to vent during the
daytime, while protecting the seedlings from nighttime lows and
exposure to the sky. Around here, seedlings will blacken with air
temperatures in the low 40s when the morning dew condenses on them.

Tomatoes did fine without bottom heat. Peppers took a lot longer to
germinate and to grow. I did eventually get peppers, but if you grow
a lot of peppers and are willing to have one seed tray with a heat
pad in the house, it might pay to give the peppers a bit more
coddling.

If you are growing tomatoes, a great method I learned about at
tomatoville.com is dense planting: you plant 5 or 10 or 30 seeds of a
given variety per pot.  This saves a lot of space, since the
germination stage requires more attention than the young-seedling
stage, and you can concentrate your resources. By the time you're
ready to separate the seedlings and plant them in their own pots
(timing is not crucial here, since tomato seedlings are tough),
they're more resilient and can get by with less care.