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Extending Minnesota's growing season

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High tunnel
High-tunnel enclosures add six weeks to the growing season for Dallas Flynn who farms near Frazee, Minn.
MPR Photo/Dan Gunderson

Just after lunch on a Tuesday afternoon, Dallas Flynn is at his farmer's market stall in a Detroit Lakes park. But most of the bins are empty as a he greets a regular customer who arrived too late. 

"What Minnesota needs is 4,000 more farmers. Not the 6,000-acre farmers, but the guy who has 40 acres, 20 acres."

"Hey, young lady. I'm sold out of everything. Sold out of lettuce, spinach, radish," says Flynn. 

Produce usually sells well at the market, but this year the demand is greater than ever Flynn says.  

That's one reason he's trying to extend the growing season and increase yields on his small vegetable farm near Frazee, Minn.  

Dallas Flynn grows a variety of traditional vegetable crops, and he wanted the benefits of a greenhouse without the expense.   Gardeners often use hoops and plastic sheeting to cover rows of vegetables in the spring. The high tunnel is the same idea, only much larger, perhaps 24 feet wide and ten feet tall. The largest one currently in use in Minnesota is 900 feet long. 

The structures look a lot like a greenhouse. Plastic sheeting is stretched across U-shaped metal pipes. The plastic on the sides can be opened to let in air on warm days. 

"When these crops get up ten feet, it's like a jungle in here," says Flynn. "When you come out here and see these bright, perfectly shaped tomatoes, sweet eats!"

The tomato plants inside are twice the size of the plants growing outside.  That's because this plastic covering adds about six weeks to the growing season by acting as a solar heater. The air temperature is warmer than outside, but just as important, the soil warms much more quickly. 

Growers talk
The University of Minnesota and the Minnesota Department of Agriculture are encouraging development of locally produced food. The recently passed federal farm bill may also help with funding for small vegetable producers.
MPR Photo/Dan Gunderson

University of Minnesota Crookston associate professor and Extension Educator Terry Nennich has been pushing the high-tunnel concept for seven or eight years. 

"This year is the first year I can really say it's explosive," he says. "People are really interested in it." 

Nennich first saw the plastic tunnels on a trip to France about ten years ago. Farmers were using them to extend the growing season on farms in the northern part of the country. 

Nennich thought the high tunnel would be a good way to increase vegetable production in Minnesota. 

Nennich has his own vegetable farm near Bemidji. He says consumers buy everything he can grow, although people occasionally accuse him of cheating when he has ripe tomatoes to sell in early July. 

He carries what he calls his bible to farmer's markets. It has dated pictures of his crops to prove they were grown locally. 

Farmer's market
Dallas Flynn says as food prices increase, more consumers are turning to locally grown produce.
MPR Photo/Dan Gunderson

There are now at least 200 high-tunnel farming operations in Minnesota from International Falls to Waverly. Nennich says they're not just producing earlier broccoli and tomatoes; they're changing how farmers think about vegetables. 

"I've got one grower who has one big tunnel full of sweet potatoes, a crop you can't grow up here with any success," says Nennich. "That's the thing with the tunnels.  We're in zone two and three here and I think we can grow a lot of crops from zone five and six." 

That means a northern Minnesota farmer in a climate zone designate by the USDA as zone two can grow the same longer season crops as a Missouri farmer in zone six.  

Dallas Flynn grows the same long-season tomato plants in his high tunnel as a farmer might grow in Florida. 

Now, Flynn is stretching the concept to its limits. He's building a new high tunnel that will incorporate solar panels. The heat from the panels will be pumped underground to keep the soil warm in all but the coldest months of the year. 

Dallas Flynn
Dallas Flynn says high tunnel vegetable production is labor intensive, but very rewarding.
MPR Photo/Dan Gunderson

"Our goal is to be able to grow produce 10 months of the year," explains Flynn. "Right now we have a 120 or 150-day growing season. We'd like to extend that up to 300 days of growing." 

Flynn is retired, so he's doing this because he enjoys gardening and experimenting. 

He'd like to see more vegetables grown in Minnesota.  He says six local restaurants have asked for produce, but he can't grow enough to meet the demand. 

Flynn says based on his experience, a simple high tunnel pays for itself in one year. 

"The demand is there, what we need is more farmers.  What Minnesota needs is 4,000 more farmers. Not the 6,000-acre farmers, but the guy who has 40 acres, 20 acres. Yeah, you can make some money," says Flynn.  "You're going to have to work hard. It's like milking cows. It's a lot of work. But there's money to be made if you're selling direct to the consumer."

The interest is evident. More than 100 people attended a recent tour of high-tunnel farms in northern Minnesota and dozens of people have visited Dallas Flynn's operation this spring eager to learn about a better way to grow vegetables in Minnesota.