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Old December 17, 2009   #4
habitat_gardener
Tomatovillian™
 
Join Date: Apr 2008
Location: California Central Valley
Posts: 2,539
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Three ideas.

One, look at wintersown.org for ideas on starting seeds outdoors in minigreenhouses. The idea is to plant the seeds whenever you want, put the containers outdoors, and when the seeds are ready to sprout, they will. I used a bubblewrapped wire cage laid on the ground to start my tomatoes this year (no bottom heat), but then we don't get sustained freezing temperatures in early spring here. The main issues for me were venting on warm days, making the structure sturdy enough to withstand rainstorms, keeping the rain out, and keeping snails and slugs out.

Two, solar greenhouses are usually unheated. Orient them to face south and provide some thermal mass to collect heat on sunny days and release it at night. A couple resources I've come across lately (but haven't gotten my hands on yet) are
THE WINTER HARVEST HANDBOOK: Year-Round Vegetable Production Using
Deep-Organic Techniques and Unheated Greenhouses by Eliot Coleman (this is his newest book; he has several others on growing year-round in cold climates -- he lives in Maine)

SOLAR GARDENING: Growing Vegetables Year-Round the American Intensive Way .
By Leandre & Gretchen V. Poisson
(both published by Chelsea Green)

Three, which I think these two books address, in cold climates you need to protect the plants inside an unheated greenhouse, with frost blankets (heavy row cover), insulated panels, cloches, etc.
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