Now that spring has sprung, with daytime temperatures already reaching 20 C, Niagara grape growers will be keeping a close eye on temperature swings predicted in the local weather forecast.

Industry veteran Ryan Brewster (BSc ’03) says this was “a relatively good winter for growers’ nerves because sustained cool temperatures experienced from late December through to early March maintained good levels of winter dormancy.”

He teaches the Foundation in Viticulture professional and continuing studies course at Brock’s Cool Climate Oenology and Viticulture Institute (CCOVI) where learners are taught research-backed vineyard management and winter mitigation strategies.

Brock Assistant Professor of Biological Sciences and CCOVI researcher Jim Willwerth (PhD ’11, OEVC ’04) agrees that grapevines in the region have overwintered well and are staying winter hardy.

However, the expert on climate change and vine resiliency warns drastic temperature fluctuations at this time of year can increase the threat of injury to buds.

Vines are presently entering a period known as “deacclimation,” where warmer temperatures will cause grapevine buds to start losing hardiness.

Just as consistent and moderate cold weather in winter is good, says Willwerth, consistent and warm daytime temps in early spring can be harmful, confusing vines into thinking it is time to prepare for budding.

“The risk is that if we start getting very warm daytime temperatures in March then buds might then lose hardiness quite rapidly,” he says. “If vines then experience below freezing temperatures overnight or in the morning, which are below the level the buds can tolerate, bud death and vine damage can occur.”

Brewster credits moderate winter temperatures for the current well-being of vines and says local growers are currently anticipating near full crop loads.

Temperatures in Niagara fell to approximately -15 C to -20 C during a few short stretches in January and February but didn’t stay there for an extended period.

This contrasts with what happened in British Columbia’s wine country over the past two winters. Unusually extreme and prolonged cold temperatures in the -30 C range in the Okanagan Valley in 2023 and 2024 devastated crops in the province.

“The external temperatures in Niagara so far this winter have not reached any of those critical levels to have any major concerns from the local grower community,” he says.

Brewster has a long history of helping local grape growers react to weather fluctuations.

From 2010 to 2022, he helped run the CCOVI-developed VineAlert program. Launched in 2010, VineAlert was a flagship research program that grew into an industry outreach service available to all grape growers.

The program, which tracked bud cold hardiness throughout the dormant period from fall to spring, allowed growers to determine when to take proactive measures to save vines from freeze injury by using wind machine technology to warm up the air around the vines or adapting pruning strategies to compensate for anticipated bud injury.

In 2022, CCOVI transferred the technology to the industry by first licensing the web-based platform to the Grape Growers of Ontario (GGO) and in 2023 to the Centre de Recherche Agroalimentaire de Mirabel (CRAM-Mirabel) to run programs in Ontario and Quebec, respectively.

GGO has now launched its bud hardiness program, which is run through e-Grape and accessible by GGO members.

“It’s rewarding to see CCOVI research and innovation be so successful that it becomes widely used by the industry,” says CCOVI Director Debbie Inglis, who is also a Professor of Biological Studies at Brock. “Everything we do at CCOVI is driven by industry needs and an overwhelming desire to see the Ontario and Canadian wine sectors thrive through successful technology transfer.”