Farmers head indoors to extend season

Though Michigan is no Oregon, Adam Montri figured his experience with greenhouses there might translate into something useful for the West.

After all, he figured, being around the same latitude means about the same lighting conditions.

"We're light farmers," he told a roomful of interested people at a recent Small Farms and Farm Direct Marketing Conference on the campus of Oregon State University.

Montri is an academic specialist with Michigan State University's Student Organic Farm and manages the Hoophouse Project for the Michigan Food and Farming Systems.

A hoophouse, he said, is just another name for greenhouse or high tunnel.

His focus is on passive solar greenhouses. Read that: "unheated." Yes, even in Michigan, whose winter conditions are much more severe than those in Western Oregon.

Light farmers, he said, work to capture light and turn it into growing energy. They do this by designing the greenhouse to maximize exposure.

A major aspect of that design is setting the pitch of the roof to allow maximum light penetration. A higher roof angle increases winter light interception and minimizes reflection. The right pitch allows 60 to 80 percent of the light of enter.

The soil acts as thermal mass to hold whatever heat is captured.

"Extended cold weather impacts the temperature and crop survival," he said. "Extended cloudy weather can lead to very cold soil as well as plant damage to marginally cold-tolerant crops."

Growth continues - though at a slower pace - as the temperature dips. At 34 degrees F, for example, it may take five weeks to grow what normally matures at four weeks.