HARBORSIDE, Maine — Walking into the large greenhouse at the center of Four Season Farm on a recent Tuesday, the smell of summer is inescapable. In the large wood-heated, high tunnel structure, 10 rows of bright leafy greens are thriving and the aroma of moist earth embraces you like a warm hug from July.

But it’s mid-January and snow is in the forecast. How is this possible?

For the last 20 years, Eliot Coleman, known in Maine as the go-to guy on winter farming practices, has been commercially growing an array of cold-hardy vegetables through the winter on Four Season Farm in an unheated high tunnel and more delicate greens in the minimally heated high-tunnel greenhouse.

Despite fall’s first frost traditionally marking an end to the growing season in northern climates including Maine, farmers are following in Eliot Coleman’s footsteps, utilizing a combination of creative growing techniques to harvest fresh crops throughout the winter months.

“A lot of [farmers] felt the Common Ground [Country] Fair was pretty much the end of the season. Then we started messing around with season extension, using [crop] covering to get more growth out of things, then it became end of October and early November,” MOFGA Agriculture Services director David Colson said. “Now really there are a lot of farmers that I know [who] are pretty much farming year-round.”

Coleman has been a prominent figure on the Maine farming scene since he established his farm in the late 1960s, buying his land from well-known homesteaders Helen and Scott Nearing. Coleman is a proponent of organic farming practices and has written several books about organic farming and four-season growing. After trying a variety of winter growing techniques on a smaller scale, he began commercially growing during the winter in 1996, motivated by a desire for people to have access to fresh produce in the winter without having to buy vegetables that were imported from warmer climates.

“When we were first here in the ’60s and ’70s, at the end of every September we would turn our business over to the Californians, and that seemed like something I didn’t want to keep doing,” Eliot Coleman said.

Working with winter’s challenges

Eliot Coleman’s daughter, Clara, took over as farm manager in September, but Coleman, 78, is still very much involved in the day-to-day farm duties and is the brains behind the winter farming setup that has been slowly growing over the last 20 years.

Four Season Farm is located on 40 acres of land in the small coastal town of Harborside. Fourteen of the 40 acres have been cleared. About 2½ of the cleared acres are in vegetable production during the spring and summer. During the winter, Four Season Farm growing takes place inside of the farm’s eight high tunnels, which vary in size.

High tunnels — or their smaller cousins, hoop houses — are structures that consist of a frame and a plastic covering that are placed over an area of soil to trap solar heat and also protect the rows of crops growing inside from snow and wind.

Eliot Coleman uses a quote from Buckminster Fuller to describe growing in unheated high tunnels: “Don’t fight forces; use them.”

With winter bringing colder temperatures and shortened hours of daylight, the high tunnels help retain as much heat as possible. The warmer microclimate created inside the high tunnel mimics growing conditions that farmers in New Jersey would experience in the winter, Coleman said.

Inside of Eliot Coleman’s high tunnels are several low tunnels that provide additional cover for each row of crops. These tunnels are covered with a spunbonded cloth material that lets sunlight and moisture pass through. At night these low tunnels are covered with a plastic material to retain as much heat as possible. The effect of the low tunnel creates another microclimate shift that Eliot Coleman likened to Georgia’s winter climate.

Lifting the covering from the low tunnels, Eliot Coleman reveals rows of carrots that were planted in the fall and are waiting to be harvested — their green tops proof that while it may look like winter on the outside of the high tunnel, there’s plenty of good stuff going on underneath the soil in this created microclimate.

“There is no heat input, [it’s] just double covered [in the high tunnel],” Eliot Coleman said. “It isn’t hard to do, and I know lots of people who just do it in their backyard with a very funky little structure and it is a new game.”

While the tunnels create a warmer climate, the temperature inside still dips below freezing, especially at night, but Eliot Coleman said there are a variety of crops that can handle the cold night temperatures as long as the high tunnel can warm again the next day. Among these crops are kale, spinach, leeks, carrots, swiss chard, collard greens — all of which are among the approximately dozen winter crops being grown at Four Season Farm.

“In the middle of winter, we’re not growing tomatoes or peppers or eggplants or cucumbers, but there are all these wonderful crops, and especially spinach, that doesn’t mind freezing at night as long as it’s out of the wind and it warms up the next day,” Eliot Coleman said.

Giving the farm additional winter growing potential is its large heated greenhouse. The 36-by-96-foot structure is heated to a minimum 38-degree temperature by a woodstove while farmhands are present during the day and by a small propane heater during the night. The climate inside the greenhouse can get as warm as 80 degrees during a sunny winter day, but to prevent the greenhouse from getting too warm and harming the crops, the top of the structure can be vented to release humidity and moisture. Thriving in this greenhouse are rows of arugula, kale and lettuce.

“The benefit here is that this is local, sustainable agriculture. If we’re growing year-round we’re not having to import it from anywhere else. We have it right here. It’s good, fresh stuff. It’s relatively easy to do this as long as you have a few basics,” Clara Coleman said.

Developing winter roots

On top of a basic understanding of how winter temperatures and decreased sunlight hours affect plant growth, a key to winter farming is having the infrastructure to grow in, which Clara Coleman says can be the most difficult to conquer because of cost.

High-tunnel costs vary depending on the scale a farmer wants to grow during the winter. Clara Coleman said a simple do-it-yourself tunnel can cost about $900 to build, compared to a commercially manufactured movable high tunnel that can cost about $6,000. The more features a high tunnel has, such as automated ventilation panels, the more expensive it will be, she said.

Last winter, Noami Brautigam of Dickey Hill Farm in Monroe began dabbling with winter growing in her small hoop house. “That was primarily just selling to neighbors,” she said. “I think it’s always smart to start things on a small scale.”

For Brautigam, starting on the small scale allowed her to figure out some of the challenges of winter growing before investing resources in scaling up to a high tunnel. Last year she and her husband, James Gagne, received a cost sharing grant from the Natural Resources Conservation Service, or NRCS, to purchase and construct a high tunnel.

Before securing the NRCS grant, Brautigam sought to educate herself formally on winter farming, taking a three-day intensive course on the topic last winter through the University of Vermont. “That class was sort of the inspiration to scale up,” Brautigam said.

In February, Brautigam was awarded the NRCS grant, and she went into planning mode, figuring out when they needed to build the tunnel, along with planning the planting schedule and organization. In August she seeded her winter crops in the high tunnel to make sure they germinated and sized up before the days got too short.

This winter Brautigam is growing spinach, kale, parsley, cilantro, scallions, swiss chard and lettuce. However, a cold snap in December took a toll on her rows of swiss chard and lettuce, and the crops didn’t survive.

“[In the summer] if a certain caterpillar came and did a lot of damage, I would probably just rip that bed and start fresh right away,” Brautigam said. “One of the challenges [with winter growing] I would say is playing with the balances.”

When a crop is damaged in the summer, a farmer could reseed and would likely have success in a full regrowth before the end of the season, but in the winter, with shorter daylight hours and low temperatures — even in a high tunnel — regrowth is slow. In late November and December, when days are the shortest, plants inside of the high tunnel are primarily just surviving rather than growing, according to Colson.

The matter of regrowth is something that Eliot Coleman says is tough for farmers to work with when they are getting acquainted with growing in the winter. Given the slow regrowth, harvesting cannot be done as frequently without depleting the entire stock of crops, and therefore having to take a break from harvesting for several weeks in order for the plant to regrow.

“If you weren’t aware of that and went out to your greenhouse and harvested it all for one market, you’d be saying ‘Oh my gosh, what do I do next week?’ Well these are the sort of things you learn after time — how much you can harvest,” Eliot Coleman said.

The larger scale on which Four Season Farm is growing their winter crops allows for a rotating harvest schedule. Each week two harvests are done, but each harvest is taking only some of a certain crop, allowing the plant time to regrow so it can be harvested again in later weeks.

With only one high tunnel for all of her crops, Brautigam is going back to her weekly harvest schedule after taking a several week break to allow for regrowth. But at the scale she is growing, this harvesting frequency allows her to serve the farm’s 15 CSA members and also sell to a local restaurant.

“It feels more important in the wintertime to only harvest what you’re selling,” she said.

Producing and feeding year-round

Despite the challenges that she’s had to adapt to, Brautigam hopes to expand her winter growing in the near future by adding a second high tunnel. With fewer farms offering fresh vegetables during the winter — selling storage crops primarily, instead — Brautigam sees winter growing as filling a demand.

“One of the things is folks in Maine are buying more local foods,” Brautigam said. “And they’re asking, ‘Where can I buy greens in the winter?’”

Four Season Farm sells their winter produce every Saturday at the Blue Hill Winter Market. Clara Coleman said that within 10 minutes their spinach is sold out and within 45 minutes their fresh produce is practically gone.

But the high tunnels aren’t just good for growing in the winter months; they can also help farmers start their spring and summer crops early. By being able to seed plants in a warmer microclimate they will grow to size faster than if a farmer needed to wait until outdoor conditions were ideal.

At Four Season Farm this inter-seasonality is made more convenient by the fact that all but one of the seven high tunnels have wheels on them, making it so that when outdoor growing conditions are ideal the high tunnel can be rolled away.

This practice allows for them to have a consistent harvest year-round, Coleman said, meaning that throughout the year they will always have vegetables such as lettuce and arugula available when they go to the farmers market. The biggest change in vegetable availability that market goers will see is that by June summer crops such as tomatoes and cucumbers will also be added to Four Season Farm’s selection.

Inspired by Four Season Farm, Wolfe’s Neck Farm, a nonprofit farm in Freeport, is putting to use the movable high-tunnel model on their own property after receiving a grant last year. The farm runs a teen agriculture program, which donates the produce grown on the farm to food banks such as Good Shepherd’s Mainers Feeding Mainers program.

By being able to grow a select number of winter crops inside the new high tunnel, the farm is able to provide produce at a time of year when the need for access to fresh food increases for those who are food insecure, according to Piper Dumont, Wolfe Neck Farm education director.

“In the winter, most farms aren’t growing and so you have this increase in need in the winter and a decrease in supply,” Dumont said. “We stepped in to fill a real need.”

When Eliot Coleman began dabbling with winter growing, he saw it as an adventure in doing what others said couldn’t be done. While decades ago, fresh, local vegetables available midwinter in Maine seemed near impossible, after perfecting the techniques and working with nature instead of against it, Eliot Coleman views winter growing as an essential part of the region’s food future.

“If New England is ever going to feed itself, this is the real thing we have to learn how to do because yes, you can fill your root cellar with carrots and beets and rutabagas, but [about] now people would really like a salad,” he said.