The wild weather this winter has kept Brock University’s Jim Willwerth busy. A scientist at Brock’s Cool Climate Oenology and Viticulture Institute, Dr. Willwerth tracks the ability of grape buds to survive cold temperatures during the dormant season from October to April. He relays that information to some 300 Ontario grape growers through the institute’s VineAlert program.
“We are growing a lot of European grape varieties that are winter-sensitive and, especially in Ontario, we’re right on the cusp of where they can survive or not,” says Dr. Willwerth. Grape growers suffered big economic losses from winter injury in 2003 and 2005, prompting the industry and government to invest in more research and innovation to lessen future losses, he says.
The VineAlert program is funded by Agriculture and Agri-Food Canada and industry partners. “It’s a great research tool for us, but it’s also amazing for the growers to have this information to keep the industry viable and sustainable,” says Dr. Willwerth.
Grapes become progressively more tolerant to the cold as temperatures fall during the winter and then start to lose their tolerance as the weather warms in the spring, Dr. Willwerth explains. However, a deep cold snap or sudden temperature swings can put the buds in jeopardy. Vinifera varieties like Chardonnay, Sauvignon Blanc and Merlot “are not as hardy compared to our native varieties or hybrid varieties like Vidal or Baco Noir.”
Through the VineAlert program, researchers collect bud samples and monitor hardiness among several grape varieties at 13 sites, mainly on the Niagara Peninsula. If they believe a potentially damaging weather event is about to occur, they send an alert to area growers. Many growers now have wind machines, which they can then use to stir warmer air above the crops with the colder air blanketing the ground, in the hope of protecting the plants.
“Wind machines are expensive to run, so you want to use them wisely. But if you save a crop, they pay for themselves pretty quickly,” says Dr. Willwerth. ”It can be just a matter of a couple degrees between having a full crop on the vines and having a lot of damage.”
Researchers inspect the vineyards after a cold event to see how the buds fared. If they find there has been damage, which has been the case this year to a moderate extent, then growers can mitigate that by adjusting their pruning practices.
Some may assume that global warming represents good news for Ontario’s grape growers, says Dr. Willwerth, but that’s not necessarily the case. “What we’re seeing from our data is a lot of extremes [of temperature] during the winter, and this is very, very detrimental to cold hardiness.” A deep freeze, followed by a thaw and then another quick freeze, “that’s where the real damage can occur.”