For southeast Minnesota greens growers, winter doesn't halt their harvests

LAKE CITY, Minn. — A dark blue building sticks out from the fresh, thick snow blanketing the grounds of the Lake City Catholic Worker Farm in early December. Its south-facing wall is made entirely of glass. Despite it being about 30 degrees outside, the temperature hovers between 60 and 65 inside the building, which is one part greenhouse, one part commercial kitchen.

Baby kale, mizuna, lettuce and arugula grow in long trays. Tumeric, basil and ginger sprout from pots on the concrete floor, and on the north wall, various small citrus trees bear fruit.

Joe Ahlquist / Post Bulletin

"We are focusing on our kombucha and doing beverages," said Sara Freid, who manages the community farm with her husband, Paul Freid. "So the greens are an add-on for us. ... But we sell out when we sell it to folks, so I know that it's popular and people are craving fresh greens, local greens in the winter."

In Minnesota, winter doesn't necessarily mark the end of vegetable production for farmers such as the Freids. Winter greens producers, large and small, are using technologies like passive-solar greenhouses and hydroponic farming to keep greens growing while outside temperatures drop below zero. And with a palpable demand for fresh, locally grown winter produce, these farmers foresee more growers entering this space in the future.

"It's like, 'I need a vegetable that hasn't been shipped from California,' or something, and it's just lovely to get local vegetables," Freid said.

The Lake City Catholic Worker Farm's greenhouse was born out of a University of Minnesota Extension project to build five deep winter greenhouse prototypes across the state. With south-facing windows and 4 feet of river rock embedded beneath it, the greenhouse — completed in May 2018 — is designed to passively capture the sun's heat and store it within the rocks. Two thermostats keep the interior temperature between 50 and 80 degrees. When it gets too hot inside, fans redirect hot air from the top of the greenhouse down into the underground rocks, banking that heat for later use.

"And then when it gets cooler in the evening, it'll kick on again and do that same thing, but it's moving that hot air into this space," Freid said, adding that the greenhouse has a small garage heater that helps heat the greenhouse on very chilly days. "It's not like this high-end, technologically advanced thing that is out of reach for a lot of people."

The result is a low energy input greenhouse where Freid's family and farm guests grow winter greens and start nurturing plants that they'll transplant outside in the spring. The farm's residents eat some of the greens, and they sell the rest of the harvest alongside their kombucha at the on-site beverage stand. They sold between 50 and 60 pounds of greens last winter.

Joe Ahlquist / Post Bulletin

Freid said the space aligns with the farm's intentions, which are rooted in Catholic Worker values.

"We want to live in a way that is not taking advantage of the Earth because it is not ours, and we need to have it around for later on," she said. "We also need to live in a way that does not take advantage of communities."

Freid said she can see the deep winter greenhouse model becoming more popular, perhaps among farmers who want to keep some cash flow through the cooler months.

"Even since building it, there's been a number of people — organizations, schools and just random, individual people — who have come out to see the place and are really interested in building them for themselves," Freid said. "I think it's definitely going to become more popular."

Another small-scale production model is taking off in Wykoff, Minnesota. Rahe of Sunshine Farms, operated by Tony and Kelly Rahe, uses a very different system than the worker farm — the Rahes grow thousands of lettuce heads with no soil, minimal water and artificial sunlight in a 40-by-8-foot shipping container outfitted by Freight Farms.

The young lettuce, basil and arugula plants' roots are embedded in peat moss plugs, planted vertically in walls within the trailer. The plugs are held in place with sponges that are moistened with nutrient-enriched water. Red and blue LED lights replace sunlight, and the container's automatic climate control system can be adjusted from the Rahes' laptops or phones.

"We actually have about 9,300 plants that are currently in production, whether they're in the cultivation wall or in the nursery," said Kelly Rahe. "On top of that, we have three different microgreens."

The newly established farm just opened its online store for orders, Rahe said. Customers can place their orders online, and within the next week, Tony Rahe will bring the orders to Rochester, Preston and Owatonna for customers to pick up.

"He will harvest the orders that day and then deliver them so they'll be freshly picked the day that people get them," Kelly Rahe said.

Though the Rahes use different technology to grow their greens, they share Freid's goal of providing fresh greens to the local community.

Traci Westcott / Post Bulletin

That's what Revol Greens aims to do, too — just on a much larger scale. The company's 50-acre greenhouse in Owatonna, Minnesota, produces 30 million pounds of lettuce each year, according to Tom Thompson, Revol Greens' chief revenue officer.

"We have two sets of curtains," Thompson said. "One that helps diminish the sun when needed, and another that really acts as kind of a warming blanket, so it can completely shut down the greenhouse and keep heat in in the winter after the sun has gone down."

Revol also pipes in warm water to hydrate its greens and keep the greenhouse warm.

Courtesty / Revol Greens

"It's a constant calculation that we are monitoring, whether it be light, whether it be temperature, whether it be CO2 or humidity," Thompson said. "Every five minutes, our climate sensors are going through those algorithms and trying to optimize the climate."

The climate-controlled environment and hybrid hydroponic system (which uses some soil) get rid of the variables that come with outdoor vegetable production, making Revol's harvests more consistent and predictable. Though Revol also has greenhouses in Georgia and California and is building another in Texas, its original Owatonna operation carries the company's intent to sell lettuce that hasn't had to travel far or long to make it to Minnesotans' tables.

"If we can give more days back to all of the stakeholders across that supply chain, you're going to reduce shrink," Thompson said, referring to produce that spoils or is otherwise lost during transportation and processing. "We're going to reduce shrink because the buyers for our product are buying for delivery tomorrow, and we're harvesting today for that delivery tomorrow. That's going to be seven additional days that consumers then benefit."

Thompson said the growing appetite for local produce (and its prolonged shelf life) means there's space for growers, large and small, to enter the market.

"We do think that there will be more competition and more growth in this space, and we welcome that," Thompson said. "It gets people caring about where their food comes from and helps educate them on the process."

Traci Westcott / Post Bulletin

Traci Westcott / Post Bulletin