Experts explain just how much damage hailstorms inflict on precious vines

By / Magazine / May 26th, 2017 / 15

In May 2016, Chablis, Beaujolais and Cognac experienced a freak hailstorm. It was so out of season that France’s national farming federation, la Fédération nationale des syndicats d’exploitants agricoles (FNSEA), declared a state of catastrophe. Yes, you read that right: catastrophe.

The hail hit France’s vineyards hard right at the beginning of the 2016 growing season, and it came after a tough April that saw frost and hail damaging first buds in les vignobles. As a result, there was extensive damage that prevented winemakers from spraying their vines and led to an increased risk of disease while, at the same time, reducing the overall yields.

“Hail’s kinda one of those things — it is what it is,” says Carl Bogdanoff, viticulture biologist for the Science and Technology Branch of Agriculture and Agri-Food Canada. “If it’s super heavy, it can strip a vine clear and your season is over. It’s never black and white. It’s very spotty. So one vineyard could be totally devastated by hail and a kilometre away a vineyard can be untouched.”

“Hail can be very devastating depending on the size of hail, duration and timing during the growing season,” says Jim Willwerth, senior scientist at Brock University’s Cool Climate Oenology and Viticulture Institute. “Hail of any size can cause injury especially if it is an intense storm. Larger hail can damage more than just the tender parts of the vine, such as leaves and fruit.”

When a hailstorm hits a vineyard, the tiny (or huge) ice spheres may bounce safely off the canopy of the vines, leave little bruises on the berries or dent the vines; or hail can pierce right through the leaves, mar the flesh of the vines and puncture the skin of the berries. Such damage harms the vine.

“There can be direct effects, such as loss of leaves and fruit,” explains Willwerth. “But hail damage can also lead to increased disease, especially to the fruit, and even damage the permanent parts of the vine, leading to a longer recovery period.”

“If you get a hail storm at harvest or, say, at veraison, that can be a big issue because your fruit can get damaged,” says Bogdanoff. “So if your fruit starts to ripen, it’s changing colour then it can get detritus — you have to really get in there and protect from pathogens.”

Hail hitting the vines at different points in the season can have different effects, which kind of goes without saying. But whether or not the damage is slight (vines still produce viable grapes), severe (vineyard has limited-to-no yields but will recover in time for next year) or catastrophic (recovery may take two or more seasons) depends on timing.

“The time of year does have an impact,” Willwerth states. “Early in the season can result in damage to tender shoot and leaves, leading to defoliation and loss of flowers. Hail late in the season can cause significant loss in fruit due to tender clusters being on the vine and a lack of time for the vine to recover.”

“If you have hail in the spring when the grapes are pea-sized, then the damaged berries will shrivel up and fall off,” says Bogdanoff. “Vines seem to recover fairly well.”

With spring hail, the vines will still produce enough grapes for winemakers to recover their product. However, hail hitting the vines later in the season means there’s less likelihood for recovery, which in turn means a winery’s wine production will be smaller or non-existent.

“If it happens in May, then you’ll have new shoots come out and there might be enough time to ripen so you can still get your crop out,” says Bogdanoff. “If it happens in June, then it’ll never ripen and your season is done.”

Luckily that doesn’t mean the end of the vineyard for winemakers: the vines will recover and make grapes again in the coming seasons. “Vines are tender but at the same time quite resilient and can recover if managed correctly with sound decisions following winter injury,” says Willwerth. “Hail storms have damaged fruit and vines in the past, resulting in crop loss, however the vines rebounded well in most cases the following year.”

“So I’ve seen hail in June where it just stripped everything off the vines and the crop is just gone — all the leaves are gone. What happens is the vines will sprout out again. They’ll put out new shoots,” Bogdanoff explains. “I’ve seen hailstorms in August where five percent [of the grapes] are damaged and those will just dry up. But the vine itself will pretty much recover and send out new shoots and will grow. It’ll have reserves and all the buds will be fairly protected.”

How old the vines are will dictate how the vines recover from a severe hailstorm. “I’ve seen young shoots where the shoots are actually bruised and damaged so anything above where the hail hits the vine will essentially die off,” says Bogdanoff.

“The canes and trunks can be damaged, however in most cases normal pruning can mitigate the damage,” says Willwerth. “However, young vines may not recover as easily depending on the severity of the hail damage. Young vines that are being established need more care and are more susceptible to most extreme weather.”

Older vines have the advantage of sturdiness; their old growth and thick trunks mean that surface damage inflicted by hailstorms won’t require as much time to regrow. “For older vineyards, you’ll still have the old wood there,” says Bogdanoff. “It’ll send out new shoots so you can recover the next year or the year after.”

“Older vines will be more resistant to extreme weather with respect to moisture (excessive rain or drought) due to established root systems,” mentions Willwerth. “However, no vine is indestructible, regardless of age.”

Out-of-season climate seems to be occurring more and more often. People write it off, with a bit of a scoff, as part of global warming or climate change, but what happens if it really is a change of normal weather patterns? Will vineyards still be able to survive, especially in prestigious regions like Beaujolais and Chablis, and in young regions like Canada?

On this point, Bogdanoff and Willwerth have differing opinions. Bogdanoff believes climate change will not be the end of vineyards as we know them, while Willwerth believes it to be a great threat. Both agree, though, that growers will have to adapt and develop new technologies and practices to save their vines.

“Relative to geologic time, climate change is happening in the blink of the eye,” says Bogdanoff. “But for you and I, and the vineyards, it’s gradual. The growers are pretty smart about it. They can adapt to it. Reporters write about Napa Valley becoming too hot, but that’ll be 20 to 30 years from now. It opens up new opportunities for other regions. It’d be a shame if Napa Valley lost its perfect climate for Cab Sauv, but growers will adapt. It’s such a long-term thing, growers will figure it out.”

“Climate change is a great threat because of the risk of extreme weather,” says Willwerth. “This means that growers will have more challenges to deal with, and perhaps these will occur more frequently. As a result, innovative practices will need to be implemented in order to mitigate some of the negative impacts of extreme weather.”

Bogdanoff agrees about the extreme weather issues: “It makes it difficult if you have huge swings in climate — say, hail storms or wind storms — [which] can make it harder for growers to get their crops in. But they figure it out.”

Willwerth provides an example in the form of Ontario’s Vine Alert and Tender Fruit Alert programs. These programs exist to monitor the hardiness of vines throughout the winter, when they’re dormant, and to inform wine growers if there are any perceived risks to their grapes. The growers then go all modern, using wind machines and the like to protect their crop. “Each year is different,” writes Willwerth. “But through these programs [they] can inform wine growers on how the plants are responding to weather conditions in a very timely manner.”

Climate and weather play a huge role in the development of vineyards around the world, whether it’s here in Canada, where we have hot summers and cold (or very cold) winters, or over in France, where the weather is a bit more mild and manageable.

“Here’s a big secret: growing grapes is actually farming, so you’re at the mercy of the weather,” says Bogdanoff. He mentions that, of all the fruit harvesting out there, vineyard growers are actually a bit lucky when it comes to hailstorms. “Grapes are crushed and turned into wine. But if you have an apple orchard and you get hail, it puts dents and bruises in your fruit so you can’t sell it at the market. It becomes an issue growers have to deal with. If they get a hailstorm, they may have to spray for detritus rot and sour rots.”

It’s not all doom and gloom, though. No matter what our new normal becomes, scientists and innovative wine growers are on the case.


A freelance writer and editor, Lisa Hoekstra loves learning and trying new things. She can be found with her nose in a book or multiple tabs open on her browser as she researches the latest and greatest in the world of food, style and everything in between.

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