Many Ontario vineyards that saw their grape crops damaged by extreme cold weather this past winter are experiencing strong growth again, thanks to the mild summer, experts say.

Favourable weather conditions, such as ample precipitation and the lack of extreme heat or drought, help the crops recover from cold injuries, according to Jim Willwerth, a viticulturist with Brock University's Cool Climate Oenology and Viticulture Institute.

“It allows vines to recover from the injury and support the fruit on the vines,” he told CBC Hamilton. “The vines balance themselves. They naturally compensate for losses.”

The harsh, long winter — marked by record-breaking cold temperatures and bouts of polar vortex — wreaked havoc in local vineyards, with one Niagara on the Lake vineyards owner reporting the loss of almost all of his Syrah and Sauvignon Blanc crops.

Growers have been mitigating some of the damage by leaving extra buds while pruning, which paid off during the growth season in summer, Willwerth said.

“Even though they might not produce as much fruit as they did in previous years, they are recovering well,” said Willwerth, who also oversees Brock University's VineAlert program which tracks the survival rates of grape buds across Ontario.

Sporadic impact

Smaller yields this season are inevitable, following a winter with continuous deep freeze, said Debbie Zimmerman, CEO of Grape Growers of Ontario, which represents more than 500 grape growers in the province.

“Grapes are very susceptible to continuous cold. They can handle cold, but continuous deep cold, that's when grapes become more susceptible,” she explained.

Consumers, however, wouldn't have to worry about an empty wine rack, thanks to a record-breaking harvest from the previous season that filled the tanks with wine. And the bitter cold has a silver lining for wine lovers.

“The quality this year looks like it's going be really, really good because of the weather as well,” Zimmerman said. "It's a much smaller crop but exceptional quality."

Grapes' cold hardiness is location- and variety-specific. The latest data from the VineAlert program shows the bud survival rates range from four per cent for merlot at Lake Erie's north shore, to 86 per cent for pinot noir at Niagara Peninsula.

Zimmerman described the damage as "sporadic."

“Small sections of vineyards are going to have a hard time surviving this year. Other sections are doing really well,” she said.

Risky business

Hank Hunse's business isn't among the lucky ones.

Some varieties of grapes from his Small Talk Vineyards, located a kilometre south of Lake Ontario in Niagara on the Lake, were completely damaged by the extreme cold, he said.

To compensate the loss, Hunse said his store is expected to raise the price of the 2013 wine by up to 30 per cent.

“I'll lose customers, I know that. But it's the way it goes,” he said. “Some [customers] really want to buy local, they'll keep buying. Some will buy the cheapest from another store, and they'll stop.”

While he is planning to install some mitigating technology — such as wind machines and ventilation shaft fans to improve air flow — Hunse said this winter has also taught him that being a grape grower in Ontario, a province with unpredictable weather, can be a risky business.

"It just shows you are in extreme wine-making region. It's full of risks."

Zimmerman has a more rosy outlook.

“We grow grapes in a cool climate. There's not much else we can do when mother nature delivers a blow like she did in the winter. But the good thing is we still have grapes."

Harsh weather conditions are a great learning opportunity for grape growers that helps them get better at their craft, she added.

"What we are finding is growers are becoming much more tech-savvy and trying to apply technology to the vineyards, as you can see with VineAlerts."