Researchers study how to extend the growing season

MAFRD is looking at how well these oversize cold frames 
can extend horticultural growing seasons


A production system that extends the growing season, offers growers a competitive edge in the marketplace and potential to make more money sounds mighty tempting.

That’s why fruit and vegetable growers were out in large numbers at Hort Diagnostic Days in late July to hear more about construction of high tunnels.

This is the first year a variety of fruits and vegetables has been planted in the high tunnel built in 2014 at the Agriculture and Agri-Food Canada location in Portage la Prairie. Growers are keen to hear what Manitoba Agriculture, Food and Rural Development (MAFRD) specialists are learning.

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High tunnel production is commonplace in other parts of Canada and in northern and central U.S. where nearly every type of fruit and vegetable is now grown, even tree fruits. MAFRD staff are researching how high tunnels work in Manitoba growing conditions.

“We have a lot of recommendations from other places like Minnesota and Ontario about what to grow in a high tunnel but nothing for under Manitoba conditions,” said fruit crop specialist Anthony Mintenko, who is evaluating day-neutral strawberries, early-season June-bearing strawberries, fall-bearing raspberries and blackberries at one end of the 100x15x7.5-foot tunnel. Provincial vegetable specialist Tom Gonsalves is experimenting with vegetables such as tomatoes, cucumbers and peppers at the other.

High tunnels are like greenhouses, except they don’t have a double layer of poly, and no permanent heat or electricity. But they have a similar function — they keep cold out and, conversely, heat in.

Planting your fruits or vegetables in them can get you to the market in spring earlier and continue to supply customers well into fall, said Mintenko.

August and September is prime farmers’ market season, so any fruit crop that can keep producing at that time is bound to be in demand. But right now commercial production of late-season crops like fall-bearing raspberries is typically not feasible in Manitoba. The nights are too cool and early frosts kill them off.

“We’re trying to see if we can change that with high tunnel production, and make it profitable,” said Mintenko. A handout to growers at the workshop noted that comparing Minnesota yields to the same-size tunnel production in Manitoba, it’s anticipated that three 100-foot rows of raspberries could produce a total yield of 320 lbs. If sold at $4.50 per pint, that could bring a grower a gross revenue of $2,880 a year.

They’re also evaluating the potential for a summer-bearing yellow raspberry that in field conditions can produce a second crop later in the season if grown under warm conditions.

Other advantages of high tunnel fruit production include reduced risk of fruit rot and more uniform yields.

The high tunnel at Portage la Prairie cost about $5,000 to build, with the added side venting and a drip-irrigation system pushing the total capital cost to $8,000. The side venting is needed because most fruit crops shut down when temperatures rise over 30 C.

“It is a relatively cheap design, and doesn’t have the headroom of a lot of tunnels,” said Tom Gonsalves. But that’s a capital cost you can expect to fairly quickly recoup with if you grow high-demand crops that produce well in its warmer conditions, he said.

They’re noting a summer day difference of 5 C higher in the tunnel compared to outdoors.

There was an average of a .8 C difference in temperature noted during the winter.

“Which is not a lot but it could be as much as 5 C higher on a winter day,” he added.

He plans to plant kale in September and again early next spring because “kale is a crop where, if there’s any heat at all, it’s going to grow.”

That also means successful high tunnel production takes more than merely building one and moving varieties you’ve typically grown outside into it.

There are varieties of vegetables specifically bred for high tunnel production and these typically do very well in these higher-temperature conditions, he added.

“Most multinational seed companies have varieties of the common crops like tomatoes, peppers, cucumbers, and cool-season lettuces and spinach that have been bred specifically for high tunnel use,” he said. On July 26 it was 34.6 C.

“A lot of varieties would have trouble at that temperature, he said. “But at 34.6 C all the cucumbers did was grow faster.

By then they’d already harvested cucumbers too.

“We picked the first cucumber July 10 in this tunnel,” he added.

Waldo Thiessen, executive director of the Prairie Fruit Growers Association in Manitoba calls the research an fundamental support to growers supplying farmers’ markets and other consumer-direct markets.

“I think there’s great potential in it,” he said, adding he’d be seriously considering constructing one on his own farm if he was a bit younger. He hopes to see the research yield good data so more growers in this province can confidently start to use high tunnels to extend their growing season.

“Manitoba is behind on this. Ontario is way ahead of us and down in the eastern U.S. they’re extending their season and taking advantage of higher prices and higher yields because they can protect their plants from the elements.”

About the author

Reporter

Lorraine Stevenson

Lorraine Stevenson is a reporter and photographer for the Manitoba Co-operator with 25 years experience writing news and features. She was previously a reporter with the Farmers Independent Weekly and has also written for community newspapers in Winnipeg and Manitoba's Interlake.

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