Although today’s is the last Farm and Field column for the year, the farming season is far from over. Fall brings fields full of squash and pumpkins, late summer corn, green and red tomatoes. Farm stands will stay open on through October and November. Come December, many Island farms will shut down and farmers will turn their attention to planning for the spring, summer and early fall crops.

A greenhouse, a root cellar and glass mason jars ordered in bulk mean the Allen Sheep Farm off South Road in Chilmark remains active even in the dead of winter. Owners Mitchell Posin and Clarissa Allen are working toward making theirs a four-season farm. Maintaining an active farm during the winter supports the Vineyard farming economy and promotes Island sustainability. And for Mr. Posin, Ms. Allen and others, it means a winter of soups, sauces and salads made from backyard ingredients.

Like many other farmers and backyard gardeners, the couple have long relied on canning to make their produce last longer into the season. They make dilly beans, sauerkraut and dill pickles and they can tomatoes for sauce.

Six years ago, after reading a book by author and organic farmer Eliot Coleman, Mr. Posin designed and built a plastic hoop greenhouse with eight raised beds, sliding doors and an overhead irrigation system. The structure, located next to the farm barn, is 17-by-36 feet and uses no auxiliary heat or electricity. Inside the hoop house Mr. Posin grows several varieties of lettuce, bok choy, beets and parsley through the long, cold winter months. “We get the best salad in the dead of winter,” Mr. Posin said this weekend from inside the greenhouse where the plants were put in at the end of August.

They plant only cold-tolerant crops, including hardy greens and herbs. After the first frost, Mr. Posin stacks bales of hay against the sides of the greenhouse for insulation. On sunny winter days, he opens the greenhouse doors, letting in the winter air to adjust the temperature. When it turns bitter cold, Mr. Posin explained, the plants stage death. “You’ll come in here and everything will have turned into compost,” he said. “But then in a few days when it warms up, they come back to life. It really is pretty amazing.

“It’s about the length of light, not the temperature.” It’s also about good fertilizer. Between the beds, the farmers spread mulch, which rots down into compost; every few weeks, they turn it over onto the beds. “It’s a self-nurturing environment,” Mr. Posin said.

Three years after he built the greenhouse, Mr. Posin built an 11-by-17-foot root cellar in their 18th century farmhouse. Located off a finished basement and accessible only through the house, the cellar is used for storing root vegetables, including carrots, potatoes, radishes and beets and cold-weather keepers like cabbage. “Once you get good at this, it’s better than a refrigerator at storing things because a refrigerator dehumidifies and this humidifies,” Mr. Posin said. “The trick is keeping it cold and moist.”

Of course roots cellars are not new. “That’s why they used to dig basements,” Mr. Posin said. “Why else would you go through the effort for such a small space? Because it is life sustaining.” Before walking through the root cellar door, he gestured to the alcove next to it: an original root cellar with stone walls built in 1770.

Like the greenhouse, the root cellar is unheated. A thick, insulated door and walls isolate the cellar both from the freezing temperatures outside and from the warm temperatures in the rest of the house. Inside, an S-shaped air duct draws warm air out of the room and feeds in cold outside air. The process is called borrowing and storing. The duct borrows the cold air from outside while the insulation stores it. Mr. Posin monitors conditions with a thermometer and a hygrometer (an instrument that measures humidity). The ideal temperature for root vegetables is around 32 degrees and optimal humidity is between 90 and 95 per cent. If it is too dry, the vegetables wilt. If it is too cold, they can freeze. When a cold stretch hits, Mr. Posin cracks the door leading to the finished basement.

Through an agreement with Michael Doctor of Food Bank Farm in Hadley, Mr. Posin exchanges fertilizer for overflow root vegetables. In December he will fill the cellar shelves with clean vegetables packed into mesh plastic bags. The cellar holds between 30 and 45 bushels of produce, packed tightly. “It’s nice being part of my house,” Mr. Posin said. “I can just walk into my house and come down and eat a vegetable in the middle of winter.”

Future plans for the cellar include a drip irrigation system for moisture. One day, Mr. Posin hopes to convert the old root cellar into a wine cellar.

For more information on storing or keeping food in the winter months, check out Root Cellaring: Natural Cold Storage of Fruits and Vegetables by Mike and Nancy Bubel or one of Eliot Coleman’s books available through his Web site fourseasonfarm.com.

This column is meant to reflect all aspects of agricultural activity and farm life on the Vineyard. To reach Julia Rappaport, call 508-627-4311, extension 120, or e-mail her at jrappaport@mvgazette.com.