High tunnel help: Grow, sell your crops year-round


WOOSTER, Ohio — High tunnels — unheated, plastic-covered, relatively inexpensive structures — can grow lots of food on little land, can do it nearly 12 months out of the year even in the upper Midwest, and need fewer inputs than larger-scale, open-field farming methods.

So says Matt Kleinhenz, an Ohio State University horticultural scientist, who operates four high tunnels as part of a wider study, one aimed at finding how “peri-urban” farms — farms, usually small ones, located near cities — can best make the switch to organic farming and stay in business while doing it.

The project also involves six other Ohio State scientists.

Intensive approach

High tunnels, one of four main strategies in the study, represent the most intensive approach. They take the most management but potentially make the most money.

Kleinhenz said the greenhouse-like structures, which nonorganic farmers can use and benefit from as well, produce crops almost year-round, create a wider market “window” as a result, and, through high-value crops and local selling, bring great enough returns to make a farm profitable or keep it that way.

Less acreage

Already widely used in Europe, with growing pockets of interest in America, high tunnels “help farmers farm successfully on smaller pieces of land,” Kleinhenz explained.

High tunnels are especially good for those farms that are close to cities, where land prices are high, and where there is little room to expand.

That makes them handy on farms near cities, typically places with high land prices and little or no room to expand, he said.

In a field on the Ohio Agricultural Research and Development Center’s Wooster campus, Kleinhenz’s tunnels — now in their third year and run by project technician Sonia Walker — grow lettuce and spinach, green beans and Swiss chard, beets, radishes, and zucchini.

A typical year yields leafy vegetables — lettuce, spinach, Swiss chard and radishes — from April to June; green beans, potatoes and zucchini from June to September; and leafy vegetables again from October to January.

Planting, weeding, mulching and applying compost go on as needed throughout the year.


Each tunnel measures 21 feet by 48 feet, with four-foot straight sidewalls, which roll up to let out excess heat, and a roof that peaks at about 10 feet.

Clear plastic sheeting covers a frame of 2-inch-thick metal poles.

Wood-framed doors, likewise covered in plastic, give access at each end; they serve as excess-heat vents too.

Plants grow directly in the ground, not in raised beds, though that could change in the study in the future, Kleinhenz said.

Drip irrigation brings water since the tunnels, “like giant umbrellas,” block out the rain.


The benefits of such sheltering include potentially fewer diseases due to drier foliage and no crops lost to wind, hail or snow.

Heat and light come solely from the sun, even in winter — no supplemental heat or light provided.

Construction cost in 2003: About $3,200 per tunnel, with each about 1,000 square feet.

“It’s probably more appropriate to look at high tunnels as creating a system, rather than being an individual technique, because of what they do,” Kleinhenz said.

“They’re simple structures but they create a different farming system. Fertilizer use, chemical use, fuel use, equipment use — they all change.”

Sizes, kits

High tunnels come in many sizes, depending on the needs of the farmer or gardener, from 8- by 12-foot backyard models to commercial types as long as a football field.

They come in kits, or handy growers can buy their own materials and build them fairly easily.

However, while high tunnels “are one of the more aggressive and comprehensive ways to extend the growing season, they’re not the only way,” Kleinhenz said.

Lower-cost, less-involved options include raised beds, plastic mulches, row covers and low tunnels, alone or in combination.

Growers who want to extend their season could try those first without investing in high tunnels, Kleinhenz said.

Meantime, the peri-urban study, and the high-tunnel portion of it, will continue.

Kleinhenz describes the goal as “the best yet assembly of research-based information” on the four main strategies in the study, “packaged in such a way that farmers, if they want to transition to organic production in a peri-urban setting, can make the best-informed choice as to what’s best for them.”

Learning experience

He calls the project a learning experience for everyone who works on it, too.

“What we continue to push on is high tunnel design, management options and the sharing of results and insights so farmers and researchers can make informed choices,” Kleinhenz said.

In a state like Ohio, where increasing urbanization meets a vibrant agricultural industry, “high tunnels, or any other greenhouse technology, can be an important part of the future,” he said.

“As the situations around farmers change,” he said, “farmers need more options, and high tunnels give them valuable options.”

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