High tunnels extend Ohio's growing season
The high tunnels can protect plants from cold, wind, rain, pests and disease.
They look like greenhouses -- Quonset hut-like structures swathed in plastic that serve as cocoons for growing tomatoes, lettuce, peppers, carrots, strawberries and a whole wagonful of other fruits and vegetables.
Called high tunnels, the buildings are popping up in Ohio fields and around the country as farmers try their hand at tunnel farming.
The idea is to shield the crops from the elements and trap the heat of the sun, extending the growing season and increasing production.
"The tunnels provide a microclimate around the crops that essentially fools them into thinking it is a different season than it really is," said Matt Kleinhenz, extension vegetable specialist for Ohio State University's Ohio Agricultural Research and Development Center.
A tunnel-farming workshop sponsored by Ohio State in November drew farmers from five states and 40 ZIP codes in Ohio. Hundreds of Ohio farmers are now using the tunnels, Kleinhenz said.
David and Lisa Schacht have covered more than half an acre with three connected tunnels shielding strawberries at their farm near Canal Winchester in central Ohio.
The couple, who also grow vegetables, hope the tunnels will enable them to begin selling strawberries the first of May -- four weeks before their competitors do. They expect to command a higher price and create a following of loyal customers who will return as the season unfolds.
"Our school of thought is to moderate the environment just enough to improve our yields and our quality and our season," Lisa Schacht said.
High tunnels can be large or small. Many are about 90 feet long and 20 feet wide, with wooden and aluminum frames. Unlike greenhouses, tunnels are covered with plastic, lighted only by the sun and lack automated heating and cooling systems. They cost much less than greenhouses to build, usually about 4,000.
They protect plants from extreme cold, wind, and rain -- which can keep soil wet for days and keep farmers from cultivating it -- and they exclude or reduce pests and diseases.
The main benefit is that the tunnels increase the temperature when days lengthen as winter turns to spring, accelerating plants' growth and enabling them to mature weeks before their counterparts outdoors.
They also can keep the temperature up in the fall, extending the growing season and the plants' production for weeks after outside plants have stopped producing.
The tunnels can extend the growing season by up to four months, with two months at each end, Kleinhenz said. And they make it easier to grow certain crops better adapted to zones farther south.
Bob Jones Jr. has 30 high tunnels on his Chef's Garden farm near the northern Ohio city of Huron. With them he can raise lettuce, spinach, carrots and beets year-round.
"The restaurant chefs were wanting product when we didn't have it," he said.
The biggest challenge is keeping the tunnels warm enough through the winter, Jones said. The plants can actually freeze inside the tunnel, he said, but the crop isn't harmed as long as it isn't harvested until it thaws.
It's also challenging to control high temperatures when the sun shines. Even when it is only 50 degrees outside, tunnel temperatures can quickly soar to 80.
Owners regulate the temperature by opening the tunnel doors, installing vents or lifting and lowering the sheets of plastic. They've got to irrigate the plants, which don't get rain, but also watch the humidity, which can promote disease.
"The biggest challenge is the tremendous amount of management it takes," said Paul Wiediger, who farms near Bowling Green, Ky. "It becomes a balancing act."
He uses his five tunnels, covering 10,000 square feet, year-round to grow tomatoes, lettuce, spinach, carrots, beets, turnips, potatoes, eggplants and melons.
Wiediger has to juggle the timing of planting, growing and harvesting the various crops to make sure they're ready when he needs to take them to market. He is at the mercy of the sun; overcast days slow growth.
But he said the quality, quantity and size of his tunnel crops is far superior to what he's grown outside. And the extended season brings cash when he normally wouldn't have it.