CEDAR RAPIDS, Iowa - Iowans don’t need to depend on Florida’s sunshine or tropical climates to eat succulent spinach, fresh lettuce and tender turnips during winter months.

Hoophouses, also known as high tunnels, have made it possible to grow nearly year-round in Iowa and other Midwestern and northern states.

Unlike greenhouses, which are costly to heat, the simple, plastic-covered pipe structures take advantage of natural sunlight to extend the season for a variety of fruits and vegetables.

According to Iowa State University Extension, high tunnels were popular in Europe for many years before catching on in Iowa in the last decade.

“The hope is, you’re able to grow a crop in the off-season so your market chances improve and you get more of a premium,” said Maury Wills, chief of Iowa’s Agricultural Diversification & Market Development Bureau.

Lena Gilbert, coordinator of the Springville Farmers Market, said vendors offer fresh produce such as mixed greens, onions and beets even during winter months at the market, 15 miles east of Cedar Rapids.

“I think it makes a huge difference to get locally grown items year-round in Iowa,” Gilbert said. “They never have a problem selling out.”

Laura Krouse of rural Mount Vernon, a vendor at the Springville and Mount Vernon winter markets, uses a hoophouse to grow bedding plants earlier in the spring and for winter storage of squash and other produce.

“I think the real value of a hoophouse is for salad,” she said, noting that while the greens don’t necessarily grow in January and February, they can be ready sooner in the spring under a high tunnel.

Iowa gardeners can buy or build their own smaller versions to protect plants growing in the ground, while farmers use field-scale structures large enough to operate machinery inside.

Prairiewoods, a spirituality center in Hiawatha, offered a workshop earlier this month on building a hoophouse.

The center’s new structure includes in-ground heating to provide extra warmth for vegetables that will be used in meals throughout the winter.

A cost-share program through the U.S. Department of Agriculture’s Natural Resources Conservation Service helped spur interest among Iowa farmers.

The department provided financial assistance for seasonal high tunnels as part of a three-year trial to determine their effectiveness in conserving water, reducing pesticide use, maintaining vital soil nutrients and increasing crop yields.

From 2010 to this year, Iowa farmers received $687,145 to help build a total of 172 high tunnels, according to the Natural Resources Conservation Service.

U.S. Agriculture Deputy Secretary Kathleen Merrigan noted in announcing the program that farmers who sell high tunnel produce benefit from the extra income and customers benefit from the availability of fresh, locally grown food.

Susan Jutz of Solon said she has used a stationary high tunnel since 2000 and more recently began using a movable structure.

Jutz, who operates a community supported agriculture, or CSA, can start spinach outdoors in the fall and move the new high tunnel over the crop when the weather turns cold.

She also protects lettuce from hot, dry winds in the summer by growing it under the protection of a high tunnel.

Greg Garbos, president of Four Season Tools of Kansas City, Mo., said high tunnels “move” a grower’s climate 500 miles.

Besides extending the growing season, farmers can control the amount of water and other conditions inside the structure, said Garbos, whose company has built at least 20 in Iowa.

Prices range from $5,000 for a 30-by-48-foot kit to $10,000 or more for a movable unit.

Garbos said some farmers see a return on investment in 18 months, adding that he is seeing an increasing amount of interest.

“It’s exploding,” he said. “Small-scale agriculture is absolutely booming.”