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People gathered by a high tunnel.

U horticulture educator Terry Nennich explaining the benefits of high tunnels or hoop houses at the University's North Central Research and Outreach Center in Grand Rapids, Minnesota. (The group is gathered in front of a high tunnel example.)

High tunnel craze

University of Minnesota Extension is working to improve Minnesota's fruit and vegetable production

October 30, 2007

Terry Nennich knew he was onto something as he trekked through the lush flatlands of Normandy, France, in the summer of 1999. The University of Minnesota Extension educator from Crookston had come to study fruit and vegetable practices and stumbled upon horticulture's version of a French revolution. The region's miniature, greenhouselike huts--known as high tunnels--blanketed the countryside. Inside, the plants were thriving; the cool spring weather wasn't an issue. A light bulb went on for Nennich, comparing everything he saw to his home climate. One might say his French discovery kickstarted the high tunnel phenomenon in Minnesota.

High tunnels, also called high hoops or hoop houses, are temporary structures that extend the growing season. The plastic-covered garden structures allow growers to roll sidewalls up and down for ventilation and frost protection. Because the system is enclosed, no rainfall enters the tunnel. Growers place plants directly into the soil and water them with small irrigation tubes under the plastic.

Nennich saw how enthusiastic the French were about this growing system. Fruit and vegetable growers now had a longer growing season; yields were two to three times the size of conventional gardens; and consumer demand for these homegrown goods, a month earlier than usual, added extra clout to what growers could charge. In addition, the protective walls greatly reduced the need for pesticides, or eliminated the need altogether, and new and different crops could be added to the mix.

"If it weren't for Terry, we would not have been able to do this," says Eldon Voigt, who, along with his wife, Melissa, grows blueberries, onions, cucumbers, tomatoes and peppers on the couple's farm, Elm Tree Fruit Farm, LLC, in International Falls.

In 2004, Voigt, a pioneer from the "Icebox of the Nation," first worked with Nennich to learn how to grow tomatoes in high tunnels. Today, Voigt sells at a roadside stand and to a local deli. However, he is most enthusiastic about a new project he and his neighbors have organized.

On-farm research provides key to growers' success

Dallas and Mary Flynn of Frazee monitor a high tunnel and participate in the U's on-farm research. In exchange, the University monitors the tomatoes and cucumbers grown in their tunnel, analyzing plant tissue, as well as soil composition, moisture and temperature.

Due to the high yields in tunnels, soil is depleted of nutrients much more rapidly and in higher quantity than in field-grown crops. Extension soil scientist Carl Rosen and his group analyze data, such as how much nitrogen and potassium is taken up in the fruit. They also study the benefits of adding soil amendments such as compost before planting begins.

"We're trying to develop a nutrient budget," he says. "Things are really progressing. The growers just have so much more confidence in knowing how to manage the crop."

For the Flynns, the biggest challenge has been explaining their growing system to customers. "I bring pictures with me every year because I get the same questions, 'Who do you buy your cucumbers from?'" says Dallas Flynn, who sits on the board of directors for the Minnesota Farmers' Market Association. "The beauty of it is when they find out it's locally produced by me. They love that."

"We've started a community farmers' market with 10 vendors," says Voigt. In late June, their community market officially opened, selling locally produced goods Saturday mornings in the lots outside Backus Community Center in International Falls.

High tunnels didn't spring up in Minnesota overnight. Three years of collaborative research by Nennich, Extension soil scientist Carl Rosen, engineer Jerry Wright, and retired research horticulturist Dave Wildung, as well as on-farm research, helped lay a solid foundation. Then in 2004, Nennich and coauthors finished the University's manual on growing in high tunnels. There are an estimated 150 high tunnels in use throughout the state, according to the group.

Three high tunnel experts from the U
Extension engineer Jerry Wright (L), horticulture educator Terry Nennich, and soil scientist Carl Rosen (front)

As the tunnel craze spread in the Gopher State, the number of farmers' markets also began to climb. Today, there are well over 100 active farmers' markets in Minnesota.

"Working with Terry and the U has really changed everything for us," says Voigt. "I didn't even see myself getting into farming, much less starting a community market."

For more information on commercial vegetable and fruit production in Minnesota, see University of Minnesota Extension.