Eating a variety of locally grown foods year-round is nearly impossible for most people. Although spring, summer and fall often yield an abundance of fresh produce, dreary winter days force consumers to get their five-a-day fruits and vegetables from cans and faraway places. 

This frustrates locavores––people who eat locally-grown food––as well as farmers who’d like to sell produce year-round. Although there are a handful of techniques for growing produce during the cold winter months, most of them—such as greenhouses heated with propane gas—are not exactly environmentally or economically, friendly.

Farmers at Michigan State University’s student organic farm are getting around this problem with passive solar hoophouses, also known as passive solar greenhouses, high tunnels and unheated greenhouses. These terms are used interchangeably to mean structures used in year-round farming, explained Adam Montri, hoophouse project manager at Michigan Food & Farming Systems and hoophouse specialist at the student farm.

Hoophouses maximize winter production by capturing light and warmth in the colder months, Montri said. Unlike traditional greenhouses, hoophouses don’t use electricity-generated heat. “That is the main, and a very important, difference,” he said.

Hoophouses are typically made of two layers of plastic, as opposed to the single layer used for greenhouses. This double layer retains more heat  and is so effective that sometimes the hoophouses get too warm, even on the coldest of days.

"If we were to keep the hoophouse vents closed on a sunny day, even if it was zero degrees or lower outside, we would quickly have temperatures above 100 degrees,” said Tomm Becker, assistant manager at the farm. “We regulate this temperature with the vents and attempt to build up enough heat in the hoophouse to last us through the cold nights when the sun can provide us no warmth.”

During the rare occasions when Michigan sees cloudy, below-zero days, the younger, weaker plants are moved to one minimally-heated hoophouse. It’s heated with propane, but Montri points out that it’s used only a handful of times per year.

“The majority of farmers that I work with around the state [who use hoophouses] do not use a structure like [the heated hoophouse],” said Montri. “We use it because when we first started we didn’t just move from heated production to unheated production. Like most things, there was a learning and development process that started with a heated greenhouse. As we continued to learn, we gradually decreased the temperature in that structure.”

Plants grown in hoophouses are hardy and can put up with having their foliage repeatedly frozen and thawed. These include plants of smaller varieties and those intentionally grown small, which are better at handling the cold. Baby salad mix is often grown in the hoophouses during winter because it’s always harvested before reaching maturity. Some plants, like spinach and kale, are actually tastier the more they freeze and re-freeze because the process causes the sugars to concentrate, making them sweeter.

Spreading the Word
The student farm started with four hoophouses during its first year of production in 2001.

In 2006, the hoophouses proved so successful that the farm added a fifth house to use for demonstration and experimentation. Since then, those at the farm have reached hundreds of farmers through workshops on organic agriculture and season extension, both in Michigan and throughout the Midwest. Currently, the student farm, along with the C.S. Mott Group for Sustainable Food Systems at Michigan State University, Michigan Food and Farming Systems and Michigan State’s Project GREEEN (Generating Research and Extension to meet Economic and Environmental Needs) are involved in an on-farm research project with 11 farms throughout Michigan.

 
"While we do not have a total number, we can say that we know of at least 50 plus hoophouses that are in use on farms around the state,” Montri said.

Nic Welty of Suttons Bay, Mich., is one of those farmers. He heard about passive solar hoophouses as a grad student at Penn State University.

“I liked the idea of four-seasons growing [and] not having to use an extra energy source or fossil fuels [in fertilizer] to grow,” said Welty. “With the hoophouses, you’re essentially working with what you have.”

The hoophouse boom is not  restricted to Michigan. Montri believes there may be growers in every state using these structures. In northern climates, the houses are most often used to extend warm-season crops and to produce crops year-round. In southern states, they’re used to keep rain from mitigating fungal and bacterial diseases and to extend the season. “We even know that there are some in use in Alaska,” Montri said. 
Despite the popularity among farmers, hoophouses are far from perfect. Montri explains that most problems are related to a lack of markets for winter produce. But with the local food movement warming up, that could change.

It also takes time for new technology like passive solar houses to catch on, he added. "There is also a learning curve that comes with using any new piece of equipment and we have heard from many farmers that it takes some time to develop the skills necessary to operate these structures. In the passive solar hoophouses there is almost constant planting, seeding, transplanting, and harvesting occurring throughout the majority of the year.”

Despite the extra work, farmers are generally satisfied with hoophouses, Montri said. This includes Welty, who recently enjoyed a successful season.

"Although we kind of had a late start this year, we had good production,” Welty said. "The hoophouse has worked out very well and I’m very happy with it.”

Student farm participants are working to improve hoophouses, as well as experimenting with other techniques to extend the growing season.  Starting in the spring of 2008, monthly on-farm field walks will be offered.

The reasons for spreading the word about season extension are simple, said Montri. "The health benefits as well as the additional farm income generated by year-round production have the potential to improve health in Michigan while simultaneously promoting farm viability through increased income,” he said. "We’re happy to share what we have learned thus far and look forward to continuing to learn from farmers we partner with throughout the state." 

Hailey M. Schaldach is a first-year journalism student at MSU. This is her first appearance in EJ Magazine Online. Contact her at schalda1@msu.edu