US (MN): 'Deep winter' greenhouse grows veggies year-round without a crushing electric bill

Nothing should be growing this winter day on these frozen, rolling hills. Yet here are green vegetables, kale and lettuce, growing in near-90 degree temperatures. They’re thriving in a specialized “deep winter” greenhouse, letting farmers Tom Prieve and Sue Wika grow fresh vegetables year round — without a crushing electric bill.

Their plants survive largely on natural winter light. Fans force rising heat down into a rock storage area, part of a passive solar heating system that captures the day’s warmth and releases it at night. On cold nights, a gas heater kicks in to help keep the temperature at 42 degrees. There are no banks of artificial lights.

It’s a different kind of greenhouse, mixing technology and old school ingenuity to create an energy efficient winter farm. University of Minnesota researchers say the idea is starting to take off. About two dozen deep winter greenhouses can be found now in Minnesota. Many more are in the planning stages. A deep winter growing association will soon give winter gardeners a place to share what they’re learning.

The small operations can be put up and run without spending a lot of money. Wika and Prieve’s $5,000 winter greenhouse near Ashby is built like a lean-to against the south wall of the barn. Clear plastic panels cover the south wall, which is slanted at a 60 degree angle to best catch the midwinter sunlight. Next year a wood stove will help fight the overnight chill.

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