Winter growing in NH

Olivia Saunders

Winter in New Hampshire may be long and cold, but for some farmers, the harvest never stops. As daylight fades and the march to winter begins, gardening can feel far away. This is the season when potatoes and winter squash dominate and when soup season starts trending on social media.

Winter growing, the practice of producing fresh vegetables during the cold months using protective structures like high tunnels and greenhouses, has become an essential tool for New Hampshire farms. It helps enterprises maintain cash flow during the winter, keeps employees working year-round, and gives customers access to fresh greens alongside storage crops.

Spinach and other hardy vegetables fetch premium prices during winter, with a single high tunnel generating between $10,000 to $20,000 in revenue, making winter production a key strategy for farms seeking to stay competitive. To make this possible, farmers rely on a range of season extension tools designed to shield crops from the cold.

Season extension refers to techniques that allow crops to grow longer by protecting them from cold. In the Northeast, farmers use greenhouses, unheated high tunnels, cold frames and cloth row covers. These methods help insulate crops from harsh conditions. A high tunnel, for instance, will help trap the warm air from the daytime sunshine, keeping the crops up to eight degrees warmer during the nighttime cooldown. In fact, most commercial farmers pair the use of a plastic-covered structure with a series of floating row covers.

Mountain Heartbeet Farm in Tamworth has relied on season extension from the start. For farmer Joanne Ducas, the owner, winter greens are a cornerstone of her business.

“People are hungry for anything green,” she says, “and providing it feels like a special service to the community.”

She also finds personal joy in the work.

In December or March, when the fields outside are buried under a blanket of snow, she steps into a greenhouse full of vibrant crops and feels as though she is tending her own private garden, one she can share with others. Winter greens can also complement storage crops such as potatoes and squash, creating the diversity she believes is needed to keep markets lively through the winter. Customers, she notes, “aren’t coming back just for another bag of potatoes they could frankly buy at the supermarket, but for vegetables that taste fresher and more vibrant.”

Financially, winter sales don’t match the pace of summer, but they offer steady support. Ducas estimates that about 20% of her revenue comes from cold-season growing. “My farm could survive without winter vegetable sales,” she says, “but they help pay the bills and provide a comfortable buffer, while keeping Mountain Heartbeet’s name in front of customers year-round.”

Season extension requires careful planning. Crops must reach the right growth stage before the “Persephone period” in late October or November, when daylight dips below 10 hours and plant growth slows. Hardy crops like kale, spinach, tatsoi and baby brassicas are most reliable and should be seeded six to 15 weeks before this point. Chicory, arugula and mizuna also perform well, while carrots, lettuce, chard, radishes and turnips can be more challenging.

Root crops offer another option. Parsnips planted in June can be harvested in the fall or left until spring, when their taste is sweeter, as starches are converted to sugars in response to freezing. Carrots behave similarly. Beets and turnips can be harvested late into fall, though many farmers simply store them through winter.

If you are looking to stretch your harvest and experiment with lesser-known crops, whether you are a home gardener or a commercial grower, you can try your hand at radicchio or Belgian endive. Both start outdoors during the main growing season, but the real magic happens after you dig them up, roots and all. By relocating the roots to a cool, dark spot inside your home, you can force a second growth phase and enjoy crisp winter vegetable greens long after your garden has gone dormant.

If all of this fails, you can always visit a winter farmers market to get a taste for a cold-hardy vegetable.

Olivia Saunders is a field specialist in fruit and vegetable production with the UNH Cooperative Extension, Food & Agriculture Program.