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Under the (Plastic) Dome

Hoop houses may look like simple plastic structures, but they offer great advantages for a variety of agricultural industries

By Laura Beil, Writer

Posted Jan. 6, 2015

To those who are not true hoop house aficionados, these semicircles of plastic and piping might not seem like impressive structures. Looking something like giant white caterpillars, they are low-tech artifacts in a high-tech world.

And yet, for all their quiet simplicity, hoop houses are the leading edge of a farming revolution. One by one, especially for farmers with small- and mid-sized operations, hoop houses are transforming agriculture in the United States. By offering easy-to-provide shelter from cold, rain and pests, the structures allow crops to thrive in conditions that might otherwise spell certain failure. Safely protected, plants can sprout early, bear late and be less susceptible to disease.

Steve UpsonSteve Upson, soils and crops consultant, has been promoting the benefits of hoop house gardening for nearly 20 years.

"They've worked for us, and they're working for our growers," said Steve Upson, a soils and crops consultant with the Noble Research Institute, who has been working with hoop houses for 19 years and authored a book about their construction. "I don't need to proclaim the good news anymore. The gospel is out there."

Even the United States Department of Agriculture (USDA) has joined in the hoop house hoopla, offering cost-sharing incentives for construction. So far, more than 6,000 hoop houses (which are also called high tunnels) have been funded through the USDA's Natural Resources Conservation Service. In 2010, a cluster of hoop houses were installed in the garden on the grounds of the White House.

The idea for hoop houses was inspired by traditional greenhouses, which have provided tender plants with a climate-controlled perfect day, every day for likely hundreds of years. The problem with greenhouses is that they are made of glass. Glass is expensive. Plastic is cheap.

Beginning in the 1950s, plant researchers began to experiment with making a variation on a greenhouse from plastic. "It had limited use early on," Upson said. "In the vegetable industry, they were used to grow transplants for field production." Along the way, someone got the idea of covering transplanted crops with hoop houses, offering a simple shelter over the soil that would help nurse plants along for the entire season.

To support the structure, engineers used arches of metal or plastic piping anchored in the ground. The result was something that looked much like the old wartime Quonset huts. The name hoop house is a reference to their shape. Not only was a hoop house economical, a couple of motivated guys could put one up over a weekend.

With hoop houses, spring and fall stretch out longer. Winter crops can become viable year-round. The weather outside might be frightful, but underneath a dome of visqueen, plants can remain frost-free.

While the idea has been around for a half century, Upson said hoop houses have gotten newfound appreciation from two new consumer trends in agriculture: local and organic. With a hoop house, plants that might be out of season come the end of fall can be grown locally, Upson said. Or they can be started early.

"It's changing how we think about local foods," Upson said. Crops like cucumbers, tomatoes and peppers can start early and stay late. Cool-season crops like spinach and other greens might be grown throughout the year if temperatures don't take too much of a plunge. In the northern United States, a locally grown tomato in October or fresh spinach in December might not be possible were it not for a hoop house.

University students constructing a hoop houseUniversity students construct a hoop house based on a Noble Research Institute design.

"Generally speaking, a hoop house placed over a field can extend growing by two weeks to a month on either end," said Joe Buford, a resource conservation specialist with the USDA's office in Stillwater, Oklahoma. Come early spring, the climate under a hoop house in Oklahoma suddenly becomes as balmy as San Antonio, Texas. "In a competitive market, if you can have your product ready two weeks before the next person, you can market your product so much easier," he said. And crops that arrive in times of high demand and low supply can command higher prices.

But Upson said the benefits of hoop houses go beyond season extension. They offer protection from piercing winds and up to nickel-sized hail, he said, making them especially useful for crops like cut flowers where marketability is solely dependent on a flawless appearance.

Given the low-cost benefits of hoop houses, researchers at Noble are experimenting with ways to make the most of these plastic prizes by changing the shape slightly to allow more shoulder or head room, and adding shade cloth and vents that can keep temperatures down in summer months and shield against sunburn.

The USDA cost-sharing program stipulates that they must be used under natural conditions. Buford said that still leaves a lot of latitude. Some growers are boring open pipes deep into the earth to provide geothermal heating.

Since hoop houses make the most of nature, the structures are popular with organic farmers as a chemical-free means of pest and disease control, Upson explained. While the plastic won't keep out small bugs like aphids that can easily creep underneath, hoop houses can form a natural barrier against larger pests like grasshoppers and beetles. Rot and mold are less of a problem because the tunnel can keep plants dry during excessive rain.

Upson expects to see more farmers hooping it up as word spreads. "It's an exploding industry," he said. "The systems work. You have an element of control that's affordable."

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