Dan Botkin has an active love affair with hoop houses. On his 3-acre Laughing Dog Farm in Gill, he has a walk-in hoop greenhouse that produces food all year long. There’s even a fig tree! Wonderful as it is, a big hoop house like his can be expensive and difficult to construct. Humans tend to seek complicated solutions when simple ones will do, Botkin says.
At the NOFA conference last summer, he gave a workshop on low hoop houses or tunnels (he has 12), which give “so much bang for the buck.” They are simple to build, low tech and inexpensive.
Botkin describes low tunnels as “magical,” yielding harvests of fresh vegetables during the freezing cold of our New England winters. He credits Eliot Coleman of Maine with inspiring growers like him to push the limits of winter growing. Botkin has developed a formula over the years.
First, select cold-hardy plants, including: brassicas like kale, broccoli, and turnips; chard and beets; spinach and lettuces; endive and chicory; arugula; Asian greens like tatsoi; alliums like leeks, shallots, and garlic; root crops like carrots and parsnips; and even flowers like calendula and snapdragon and herbs like cilantro.
Unlike vegetables grown in the summer, plants grown in the fall, winter and spring will seldom bolt. Some of the most cold-hardy — like tatsoi, arugula, kale and leeks — can freeze solid and come back to life. Their sweet sap works like antifreeze, Botkin says. They cast off moisture from their cell walls and go into a protective wilt, then suck it back up when the temperature goes above freezing. Each time they freeze, they get tougher.
The second part of the winter harvest formula is: provide layers of protection. What makes plants die in winter is not just the frost and cold, but the drying and burning impact of the wind, Botkin says. Just creating a windbreak like a low tunnel improves the odds. More plants survive if additional layers of protection, such as cut-off plastic milk jugs and non-woven row cover, are added as well.
The third part of winter harvests is aggressive timing, which I find difficult. Who wants to hustle those fruit-laden tomato and zucchini plants out of the way in August to plant lettuce and spinach? But Botkin says you need to have robust plants by the fall, to “hit October with momentum.” For winter harvest, begin planting in August, and ramp up in September and October. By November it is too late.
Botkin has made low tunnels from a variety of plastic pipes and wires, using whatever he had at hand. But the sturdiest and longest-lasting framework for low tunnels is made from 3/4″ galvanized steel tubing, which costs around $3.40 per 10-foot length. Since the tubing is straight, you need to bend it. Botkin has created a homemade bender out of plywood, and it takes about three minutes to bend each pole. He offered workshop participants the use of his bender in exchange for farm help or a “love offering.”
Taking him up on his offer, I bought six pipes for my 10-foot-long hoop house and, love offerings in hand, journeyed up to Laughing Dog Farm with my friend Tina. Botkin demonstrated the bender and got us started. Bending steel pipes makes you feel strong, but I was sore the next day!
To assemble the low tunnel, Nick and I inserted foot-long stakes of 1/2″ plastic pipe every two feet on both sides of the hoop house, and slid the steel pipes over them. To hold the structure together, Botkin suggests using three parallel purlins, lashed on to the hoops with strips of cut up T-shirts. To help the tunnel shed snow and water, the purlin at the peak goes on the outside of the hoops, and the ones on the sides are fastened inside the hoops.
The tunnels are sturdy. As Botkin says, “Weak stuff lashed together makes strong stuff.”
Finally, we clipped on plastic sheeting. Voila! In future years we might do what Botkin does, and dig a trench down the middle to make a foot-wide crawl path and heap the soil along the sides to make 2 1/2-foot-wide raised beds. As he crawls through the low hoops tending his crops, Botkin says he nibbles on a leaf here and there in his “snack shack.”
A few challenges with these low tunnels are: 1) temperature spikes on warm sunny days can cook seedlings; and 2) heavy snow loads can make them collapse. In addition, because there is no lighting beyond what the sun provides, plants stop growing in the middle of winter. But in March, a time when stored vegetables in the cellar are getting old or running low, the plants in the tunnels will burst back to life and you’ll have plenty of fresh greens.
Botkin’s mission is not just to grow and market vegetables, but also to spread inspiration and learning. His workshop and visit to his farm sure got me excited about growing hardy plants to harvest in the winter, using sturdy and easy-to-assemble low tunnels. Bring on the kale!
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