PAGE B6 –– MARCH 2012 THE GROWER
ONTARIO FRUIT AND VEGETABLE CONVENTION 10TH ANNIVERSARY
The pros and cons of growing raspberries in tunnels Come April, raspberries in greenhouses for example, will exhibit signs of stress in white drupelets. If the glass of the greenhouse is whitewashed, the issue will be solved. For those experimenting with raspberries in tunnels, the question soon becomes how to schedule dormancy. Dale says that a chilling model has been developed to reliably shut down the root zones to induce dormancy. Such success has been replicated with different raspberry varieties. “We’ve been quite excited about how we can change the morphology of the raspberry cane,� says Dale. In view of this encouraging research, why haven’t more Canadian growers adopted tunnels for raspberries? That’s a question that Doug Balsillie has
growing raspberries. He estimates that $2.75 to $3 for a half pint is required to be profitable. With both his spring and fall raspberry harvest retailed at the farm gate, he says there’s a limit to interest in berries when so many other fresh fruits are competing for the consumer’s dollar. There’s no money to be made in the wholesale market. So yes, it’s technically possible to grow higher-quality raspberry varieties such as Tulameen in these environments. But growers need to evaluate how much they can retail. Whether greenhouses or tunnels, the controlled environments are promising for a tender crop that’s been mostly pegged to the harvest window of July. With changing weather patterns,
Cravo and Voen are two manufacturers of retractable roofs which are revolutionizing how raspberries are grown. Photo courtesy of Adam Dale.
Here’s a new word for the popular game of Scrabble: drupelet. Not familiar? Any raspberry grower will know that the cluster of soft, edible fruit is called a drupelet. And a drupe is the botanical term for the fruit in which the outer fleshy part surrounds a shell. All of this word play becomes serious when University of Guelph, Simcoe researcher Adam Dale points out yet another surprising fact. Raspberries grow very well in tunnels and greenhouses. These controlled environments mimic the clearings of woodlands where the sun is dappled, root zones are warmly sheltered and rainwater is filtered through a leaf canopy. “In Europe, all raspberries are grown in tunnels – end of story,� says Dale. The research shows clearly that yields can be
improved by 20 to 80 per cent for the fresh market. Here’s what tunnels can provide. First, the mature crop is
“
In Europe, all raspberries are grown in tunnels – end of story.� ~ Adam Dale
protected from damaging winds. With controlled irrigation, fungal diseases are kept at bay. Leaves don’t get wet so there’s no spread of spores. And as a result, ripe fruit doesn’t get mouldy. Research also shows that tunnels prevent the root rots that are so common in raspberries of the Pacific northwest. In fact, the soil temperatures of the root zones have been found to be optimal at 25 degrees Celsius. Whether floricanes or primacanes, raspberries can be encouraged to bear fruit twice in a season, based on proper modification of soil and ambient air temperatures. The downside, Dale admits, is that high air temperatures promote such pests as mites, thrips and aphids -- all of which can extract their pound of juicy flesh. Recent research has also shown the interaction of light and ultraviolet rays on raspberries.
ONTARIO LAVENDER
ASSOCIATION
THE SCIENCE OF LAVENDER FRIDAY, MARCH 30, 2012
SAVE DATE
WHAT An in-depth seminar focused on innovation, research and the challenges faced when growing lavender
-----THE-----
Raspberries thrive in controlled environments which mimic a woodland clearing.
WHEN
Learn from Experts in the Industry
Friday, March 30, 2012 9:30am-3:00pm
WHERE
Members: Free Non-Members: $50.00
Quality Hotel & Suites
This project is funded in part through the Agricultural Management Institute (AMI). The AMI is part of the Best Practices Suite of programs for Growing Forward, a federal-provincial-territorial initiative.
580 Bruin Blvd., Woodstock, ON
FOR MORE INFORMATION
ontariolavenderassociation@gmail.com www.ontariolavenderassociation.org
addressed, but with greenhouses, not tunnels. At Harrow, Ontario, he’s the owner of the most southern orchard in Canada. Balsillie doesn’t need the extra heat units yet a decade ago, he started experimenting with raspberries in a small greenhouse. “We’ve gone from a very intensive to minimalist system,� he says, with the realization that all the labour barely pays for the high cost of
tunnels promise protection against the elements. However, Dale points out that while temperatures may have changed, light hasn’t. Nor has precipitation. If entrepreneurial growers can manage the production parameters, they are one step closer to developing yet another local crop. Just one caveat. Mexico is rapidly developing a raspberry industry with retractable roofs.