Jumping Through Hoops:
Farmers Take It Indoors To Offer Fresh Greens All Winter
by Cynthia Graber

At Natick's Community Farm, breath hangs in the air in crystalline clouds. Snow paints the quiescent fields and piles up in soft pillows against the sides of a domed structure, covered in plastic. But inside the small, sun-heated building-called a hoop-house-the air is temperate, almost warm. Out of the earth sprout brilliant leaves of greens such as kale and chard, adding a splash of color to the pale winter scene.

For generations, New Englanders devised methods for feeding themselves throughout the frost-bitten months. In recent decades, however, the solution in the winter-and, in fact throughout the year-has been simple: Ship produce from warmer climes.

But as interest in local food has grown, along with an interest in food quality, environmental sustainability and supporting local farmers, this method has been questioned. Now, consumers are once again wondering:

How can we eat locally throughout the winter?

More farmers and consumers are preserving food, or burying storage crops in root cellars. But what about fresh produce? Can desperately desired greens be grown without huge energy inputs throughout Boston's frigid winters?

The growing consensus is that yes, they can. And it's not as crazy as it might seem.

Traditional heated greenhouses demand a significant amount of fossil fuels to keep warm. The Natick Community Organic Farm has three different versions of what are sometimes called passive solar greenhouses, growing spaces heated by the sun. The most elaborate has a sharply pitched glass roof and a concrete floor. Hidden below that floor are rocks, and a series of pipes and blowers transports the warmest air from the top of the greenhouse to the rocks under the floor. That air heats the rocks, which then release their heat overnight.

One step down in complexity is a plastic-paned greenhouse off the barn, where plants are grown in flats on benches.

The most basic version of all, and the one most frequently adopted by farms in the region, is the freestanding hoop-house over soil. It looks like half a tunnel of flexible plastic stretched over a domed or peaked supports, or "hoops." The simplest hoop house might have only one layer of plastic. Two layers of plastic, with fans blowing an insulating layer of air between them, provide additional warmth.

While two layers of plastic might seem insufficient to shield against the ravages of storms and plunging temperatures, that shield can provide significant protection. The plastic guards plants from cold, drying wind. Inside, the sun heats the air during the day, and the plastic shielding traps that heat. On a sunny day, while temperatures outside may dip into the 20s, inside they may soar to a relatively broiling 60 degrees. The soil stores the warmth from the day and retains it into the evening, heating a cushion of air around the crops.

Eliot Coleman, winter farming guru, author of The Winter Harvest and owner with his wife, Barbara, of Four Seasons Farm in Maine, says that a one-layer plastic greenhouse in Massachusetts will mimic the climate 500 miles south in Maryland. Two layers of plastic transport a farmer all the way down to Georgia.

A variety of greens can flourish in these sun-warmed tunnels: chard, kale, mizuna, chicory, tatsoi, bok choy and spinach, whose extra-sweet winter leaves evoke raves from area farmers. Spinach, explains Coleman, acts like a winter annual: In nature it germinates in the fall, grows through the winter and goes to seed through the spring. In New England it simply needs sheltering from fierce storms. To further enhance cold tolerance, farmers and seed companies today are breeding greens to select for those that thrive in the chill.

Says Coleman, "People have a sense that when the first frost comes, and you can no longer grow tomatoes and peppers and sweet corn, life is over. But these wonderfully hardy greens are crops that Europeans have been feeding themselves in the winter for thousands of years.  Here, with a little protection, you can eat them all year 'round."

The ground, and the plants, do in fact freeze on some of the coldest nights. When this happens, picking greens first thing in the morning would cause tiny internal ice crystals to pierce the plant's cell walls, turning them into mush and subject to a quick rot. But the cells of these hearty greens are sturdy enough to survive the ice crystals if left untouched by wind or hands. When morning comes, sun streams into the hoop-house, melting those crystals. By 10 a.m. or so, the leaves will have thawed out and are ready for harvesting.

In an unheated hoop-house, January is considered the most difficult month, as days are so short and cold that many plants grow too slowly for regular harvest. During that time, the hoop-house acts as a refrigerator and protects the plants under its cover. But by February, as sunlit hours start stretching into the early evening, plants respond by again sending out new shoots of green.

Julie Rawson, farmer and owner of Many Hands organic farm in Barre, Massachusetts, says that she became interested in winter farming due to her son's prodding, as he'd been reading Eliot Coleman's books. They have four plastic-coated unheated greenhouses. In the early fall they plant winter greens to harvest in November and December for commercial sales. They now harvest for their own use through February, and then in the spring plant tomatoes, peppers, eggplants, cucumbers and melons.

Rawson has confronted many challenges: soil fertility, keeping the structures from blowing away, learning when to roll up the plastic sides in the summer to cool the hoop house down, or to let the breeze through to help pollinate but at the same time keep out disease. "It's really a science," says Rawson.

Farmers fill all the seats and lean against the walls and in the doorframe at the winter farming session at the Northeast Organic Farming Association's winter conference. Ryan Voiland, standing at the front of the room in a vibrant Red Fire Farm T-shirt, guides the attentive crowd through images of winter greens as he discusses the challenges-physical and economic-of growing in the winter. Voiland has perhaps the largest commercial hoop-house system in Massachusetts.

On his 80-acre organic farm in Granby, Massachusetts, Voiland has set up five steel-framed permanent structures covered with two layers of plastic. The greenhouses are equipped with small heaters and blowers for the insulation between the plastic layers. In two of the solar greenhouses, he adds heat on the coldest nights to keep the temperature just at or above freezing.

Voiland discusses the structures' construction, soil fertility and nutrition, and when to plant. Spinach, for instance, may take several months to grow in colder months and should be planted in September and October, so it's nearly full-sized in December and can be picked through February. As planting times are perhaps one of the most critical parts of winter harvesting, Voiland pulls up his charts that represent the rows in the greenhouse, with details about exactly what gets planted and harvested when. Last winter, Voiland grew almost 4,000 pounds of winter greens.

In the spring, farmers can get an early start on particularly popular summer crops, such as tomatoes, eggplant, peppers and cucumbers, bringing them to market a month before unprotected field crops would be ready. Voiland uses his hoop-houses for top earners such as tomatoes in the spring and summer.

Andy Scherer is sitting in on Voiland's talk. Waltham Community Farms, where he's a grower, has one hoop-house, which originally served to transition seedlings from a heated greenhouse to the cold ground, and as a dry, warm space to grow alliums such as garlic and onions in the peak summer months. But a couple of years ago, Waltham farmers started experimenting with planting greens in the late fall to harvest early winter, and harvesting again in March.

This is mostly fueled by demand, says Scherer, adding, "As the interest for winter shares has grown in the area, we really saw this as a way for us to use this space more profitably and get a little bit of extra season extension."

Voiland admits to the crowd that he's not sure about the economics of the system, as he invested significant funds in building the greenhouses and will continue to invest in their maintenance. He hopes that the higher prices he can charge for greens in the winter and tomatoes in the spring and early summer will help him soon pay off those costs. "But it can all be worth it," he says. He flashes a display of a stall at a winter farmers market in Northampton, verdant and overflowing with greens and root vegetables. "The demand goes up every year for these foods in the winter. This entire display sold out-all the greens were completely gone before the market was even over."

The use of hoop-houses has recently garnered national attention: In December, the USDA's Natural Resources Conservation Service (NRCS) announced a national program to support farmers in using hoop-houses and to evaluate their effectiveness and environmental benefits. Farmers in 38 states, including Massachusetts, can apply to their state offices for financial and technical assistance to construct a hoop-house. In response, they agree to spend three years carefully documenting what they grow, what it yields, the quality of the produce, the nutrients in the soil and the inputs such as fertilizers and pesticides.  Tomatoes grown in hoop-houses in New England, for instance, managed to avoid much of the blight that struck crops last summer.

"We're interested in this for a couple of different reasons. One, it'll extend the growing season," says Norman Whidman, NRCS national agronomist. "The other thing we're looking into is whether we can use nutrients more efficiently, and can we get by using fewer pesticides, and have higher-quality produce." Whidman says there has already been a great deal of interest from New England farmers.

Though Boston does not yet have a permanent winter market, options remain for consumers. Natick Community Organic Farm sells directly at the farm store throughout the winter. Natick, Wayland and Northampton held winter farmers markets this year. Red Fire Farm offered its first Deep Winter CSA. Some area stores such as Sherman Market in Somerville stock winter root crops and greens.

Jean Claude Bourrut Lacouture, farmer at Natick Community Organic Farm, strolls through his greenhouses, munching on leaves of spicy mustard and red-veined chard. "People are hungry for greens in the winter," says Lacouture. As demand grows, farmers are learning from one another's experiences to meet that demand all year long.

Cynthia Graber is an award-winning print and radio reporter who covers a range of topics, from science and technology, to environmental issues, to food. She shares her local food adventures on the blog www.wickedtastyharvest.com.