lone employee arrived in mid-February to turn on a furnace and grow lights in one of the northernmost commercial plant nurseries in North America.

Despite winter weather outside, within a few days it would warm to about 75˚F inside the greenhouse—the right temper-ature for starting begonia bulbs, followed by veggies such as leeks and onions—at The Plant Kingdom Greenhouse & Nursery, north of Fairbanks.

At Plant Kingdom, like other plant nurseries and vegetable farms around Alaska, greenhouses are essential for starting the growing season early to seize the opportunity of the long summer days during the short summer season.

Three and a half months after the first starts went in at Plant Kingdom, the staff ballooned from one to thirty-two to care for the plants that filled the six greenhouses and beyond. The snowy, south-facing hillside had transformed into colorful fields and gardens that the business uses as a wedding venue in addition to a greenhouse store.

Old timers in Fairbanks say that the first week of June is the safe time to put in outdoor plants, but Plant Kingdom founder Cyndie Warbelow says customers are asking for plants earlier. In recent years, the busiest weekend of the year has often been Mother’s Day weekend, a day that’s big in the nursery industry in the Lower 48 but was previously considered too early for Alaska’s Interior.

This year—which saw a particularly warm spring—customers started coming in two months before the start of the traditional gardening season, says current business owner Stephanie Bluekens, who purchased the business from Warbelow a few years ago. But even though climate change has generally made planting early a safer bet, it still has its risks.

Last year, for example, there was frost in the second week of June. Greenhouse operators can protect their plants from frost by bringing them indoors, but it comes at a cost. The business model is based on rotating plants through the greenhouse quickly.

“Things keep growing so you’ve got to be able to move stuff into your own outdoors and into your customers’ yards,” Warbelow says. “Things keep taking up more space, so the sequence needs to keep working in the right direction.”

Even with the chance of a late frost, Warbelow says the risks of starting early are worth it to be ready with plants when customers want them.

“I’ve seen killing frost for at least squash every month of the year. Agriculture is a form of gambling, and it pays to gamble,” she says.

“This year it was warming up gradually and I felt you’d be wasting the spring if you didn’t plant. I planted my garden the third week in April.”

Greenhouses work by bringing solar light and heat in through transparent ceilings and walls and trapping the warm air inside.

In other climates, solar heat alone is sometimes enough to grow plants that otherwise couldn’t be grown outside. But sunlight alone isn’t enough to warm a greenhouse to growing temperatures when it’s -20˚F outside. To operate in winter, Alaskan greenhouse owners often add supplemental heat sources and may insulate the greenhouses to prevent heat loss.

At Plant Kingdom, each greenhouse has two oil-fired furnaces: one to be used as a backup if the first one fails.

The first greenhouse the company starts up each year doesn’t look like a greenhouse; it’s a blocky, opaque half-building connected to a conventional-looking greenhouse. The business uses this insulated greenhouse for starts because in February transparent walls would cause major heat loss without bringing in much light.

The other greenhouses at Plant Kingdom are a mix of the traditional gable-roofed design and rounded Quonset-hut-shaped buildings. The Quonset design is especially good for letting in light but can more easily get too hot, Bluekens says. She also worries about strong wind ripping through the polyethylene plastic film walls of the Quonset-style greenhouses.

Elsewhere in Alaska, gardeners warm greenhouses using heat sources other than sunlight, including wood and natural gas. For farmers lucky enough to have access to it, geothermal energy is a powerful greenhouse heater. Hot springs allow for a winter plant oasis in several parts of Alaska, including Pilgrim Hot Springs near Nome and both Manley Hot Springs and Chena Hot Springs near Fairbanks.

Having access to hot springs allows growers to produce fresh vegetables outside their usual range and outside the usual growing season.

John Dart grew up near Manley Hot Springs, where the power of geothermal energy is on display at the greenhouse/bathhouse previously owned by his aunt and uncle. In the bathhouse, grapes and tropical flowers grow over four tubs of hot water.

Dart’s business, Dart-AM Farms, is down the road from the hot tub greenhouse but uses the same geothermal resource. A hot water well on his property warms and irrigates the farm’s six greenhouses. Dart grows vegetables on 7.5 acres at Manley Hot Springs and leases another 10 acres near North Pole. He uses the geothermal-heated greenhouses to start vegetables for both farms.

In the past, Dart has started planting in geothermal-heated greenhouse as early as January 21. But while it’s possible to grow plants that early in a geothermal greenhouse, he now starts in mid-February because of the limited daylight in January. Supplementing the lack of natural light with grow lights is expensive because of high electricity costs at the remote farm.

“What we found is that you could do it,” he says. “But we’re not pushing that hard anymore. The cost of electricity in Manley is so expensive that it really dictates what we can do economically.”

Closer to Fairbanks, Chena Hot Springs Resort began experimenting with geothermal greenhouses in 2004. At that hot springs, the water is used to produce electricity in addition to warming the greenhouses, which allows them to operate even during the darkest and coldest months. The Chena Hot Springs greenhouses produce vegetables that are served at the resort restaurant.

There are no hot springs at the farm of Tim and Lisa Meyers in Bethel, but the family has managed to create a productive vegetable farm in the Bush hub community without spending a fortune on burning fuel to heat greenhouses.

One of the farm’s greenhouses is warmed with a small Toyo stove, but for the most part the farm relies on the insulating power of the earth—both to protect plant starts from frost in the spring and store thousands of pounds of cabbage and root crops for the winter.

Even without external heat, it’s just above freezing in a basement below one of the greenhouses. During spring, the Meyers put flats of vegetable starts in greenhouses during the daytime when the temperature is above freezing. To protect against nighttime frost, they carry flats filled with the vulnerable young plants into the basement in the evening.

“It’s no fun at 9:30 at night to put things inside,” Tim Meyers says. “It’s a part of the job we’ve come to not particularly enjoy.”

Moving the plants is labor intensive, but the system allows him to start tomatoes in March and have them ready to transplant into the ground in May.

In the fall, the Meyers Farm loads storable vegetables like cabbage, potatoes, and turnips into a 19,200-cubic-foot root cellar. Like the basement the farm uses for the vegetable starts, the root cellar never dips below freezing, even when it’s well below freezing above ground. Having this storage space allows the farm to sell vegetables all winter.

The Meyers family began farming in Bethel in 2003, inspired by their initial success at gardening and a National Geographic article that identified the Yukon-Kuskokwim Delta as the last fertile region on earth that hasn’t been used for agriculture.

In addition to being in a difficult location for agriculture, the Meyers Farm is in a difficult location for commerce because of the expense of shipping their vegetables by airplane. But they’ve calculated their farm can produce more vegetables than the market in Bethel demands. Bethel has a population of about 6,000. There’s potential in the larger Yukon-Kuskokwim Delta region, which has a population of about 25,000.

Last year, the business experienced a breakthrough on the shipping front when the Yukon-Kuskokwim Health Corporation agreed to pay the shipping costs of Meyers Farm vegetable boxes to give its clients better, easier access to fresh produce.

“They found that it was way cheaper to feed people well than to buy the drugs to medicate them,” Meyers says.

The Meyers Farm shipped 2,000 vegetable boxes in 2018. This year, Meyers says he hopes to double that number.

Across Alaska, about 250 people worked with plants for a living in 2016, less than 1 percent of the state workforce, according to state statistics. That number covers a variety of workers, including farm workers, nursery and greenhouse workers, and farm laborers who do work on irrigation, fences, or farm buildings. The category doesn’t include farmworkers who work with animals, who numbered about 100.

Based on the rate of recent growth, the plant-growing worker category—“farmworkers and laborers, crop, nursery, and greenhouse”—is predicted to nearly double by 2026.