How to Build Unheated Greenhouses for Winter Harvests & Year-Round Gardening (Video)

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Video screen capture. Eliot Coleman

If you are aiming for a more self-sufficient way of life, growing your own food usually fits somewhere into that equation. For those of us living in more northerly, cold climes, small-scale food production can vary widely to adapt to shorter growing seasons and to boost production, whether it means using hoop houses, low tunnels, coldframes, or even underground greenhouses.

While extending the growing season late into autumn is an attractive proposal, there are some that contend that one can harvest certain veggies well into winter. Harborside, Maine organic farmer, author and agricultural researcher Eliot Coleman is one of these people, having taught himself how to grow food during harsh northeastern winters after years of experimentation.

Using unheated or minimally heated greenhouses, Coleman and his wife, gardening author Barbara Damrosch, cultivate the 1.5-acre Four Season Farm, producing hardy plants like carrots, potatoes, various greens like spinach, watercress, mâche, mesclun, and even artichokes year-round, on a commercial scale. Seen in the videos here, his explanation of his low-tech, experimental but proven methods is fascinating. Located at the 44th parallel, Coleman uses plastic-covered hoop houses and greenhouses to simulate growing conditions 500 miles south of his farm. Adding another supplemental layer of light, permeable material 11 inches above (a "floating row cover"), helps to emulate a climate thousands of miles south.

Timing is vital, as Coleman explains on Small Farm Canada:

Planting at the right time for your conditions and environment is also crucial, he says. “For example, the trick with winter-harvest crops is to get the seeds in the ground in September, not November, so the crop has a chance to grow and put out new leaves,” he explains. “I think of August-September as the second spring.” Successive seedings also ensure a continual harvest.

Coleman explains how to build a simple greenhouse for winter harvests here, starting at 9:09 minutes:

So now as autumn looms on the horizon, a winter harvest garden may be something to think about for diehard gardeners eager to grow some more. Check out more winter harvest gardens in Eliot Coleman's books, and at Four Season Farm.