LAKE CITY, Minn. — A greenhouse can be a serious investment in a farm. So, when a greenhouse is designed for winter growing, what do you do with it in the summer?
For Paul and Sara Fried at the Lake City Catholic Worker Farm, their deep winter greenhouse becomes a tropical hothouse in summer.
"We started out (growing seedlings) for our garden in here," said Paul Fried. "Squash and cucumbers. Now, it's too hot for those in here."
Instead, Fried and Shay O'Toole, a worker on the farm, have moved young ginger and turmeric plants into the deep winter greenhouse.
"They're tropical plants," he told Agri News . "The ginger is biennial, so the first year it's baby ginger. We'll harvest some and move the rest to the high tunnel for next year."
Inside the greenhouse, which is designed to capture the heat during cold days of winter, the air is hot and steamy. There is little ventilation in the space.
That's a far cry from Andrew Serio's greenhouse at his farm near Preston.
In the winter, Serio keeps his pair of greenhouses warm by using the sun's rays and in-floor heating circulated via tubes running through the cement.
But in the summer, computer-controlled vents and fans, and water walls — also known as swamp coolers — help regulate and dissipate the heat, making his custom-built greenhouse a four-season growing space.
Serio said his greenhouse has room for 1,400 lettuce plants — he grows them in seven-week cycles, 200 plants at a time from seeds to harvest — in hydroponic tubes. There are four leaf lettuce varieties in his greenhouse. He also has 85 tomato plants in the greenhouse with the lettuce and 240 more tomatoes in the second greenhouse.
With regular customers such as Four Daughters Vineyard & Winery, Pescara, Blue Duck and Forager, plus two grocery stores, Serio Farms needs a constant supply of vegetables to meet its buyers' needs. That means keeping the climate in the greenhouses constant throughout the year.
He also sells his produce at the Rochester Downtown Farmers Market. During the winter, he said, his hydroponics are a huge hit when so little fresh produce is available.
In the summer, large shutter vents open first, to help let the hot air circulate out. When that's not enough, fans kick in to move the air. And, finally, when the temperature keeps rising, the water walls begin to work, using evaporating water to cool the air much more cheaply than traditional air-conditioning.
"Without the water wall, the fans and the vents, it'd get to 90 or 100 degrees in here," Serio said. "These plants would burn up."
Instead, Serio can grow his heirloom hybrid tomato. He's also testing several traditional greenhouse tomatoes to see how his hybrid stacks up.
"I wanted to see if mine is producing as good," he said. "My plants are outdoing those by at least double."
Always testing and tinkering, Serio said he might squeeze in a row of quick greens like green onions. He now thinks he has his system down to keep a constant supply as long as he can keep the temperature controlled.
"We're really concerned about sustainability," O'Toole said, referring to the deep winter greenhouse and the Catholic Worker Farm's high tunnel, both spaces that use little to no energy input to provide an extended growing season on the farm.
The deep winter greenhouse is part of a University of Minnesota pilot program to test the low-energy greenhouse designs, while the farm's high tunnel is a typical example of a low-tech solution to extend the growing season.
"It's a protected space," said O'Toole, showing off the tomato and cucumbers in the high tunnel. "We can control the water. The pests are easier to control."
While the farm includes plants growing outdoors — ones raised from seeds planted at the same time — those in the high tunnel are nearly twice the size and have started bearing fruit sooner. The temperature inside the high tunnel is controlled by rolling up the side walls to let the air flow through.
"Those tomatoes will grow until late November," O'Toole said.
Between the high tunnel and the deep winter greenhouse, Fried said he will be able to keep produce coming for his buyers. He mainly sells to the Lake City Farmers Market. This winter will be his first utilizing the greenhouse.
"We should be able to demand a high price for our awesome winter produce," Fried said.
An AP Member Exchange shared by Agri News.