Wednesday, February 28, 2024

Climate change wreaks more havoc on wine growers with spring frost

Wine growers are always nervous in spring. They feel the excitement of a new vintage as the vines bud, push shoots, flower and set their clusters to produce the year’s crop. And they worry that Mother Nature may have a capricious surprise in store.

This year we’ve seen destructive hail in Bordeaux and even Provence, that sunny Mediterranean heartland of rosé. But the real drama between the promise and fury of spring occurred in New York’s Finger Lakes. A string of 80-degree days in late April sent vine shoots into action, and by mid-May the shoots averaged four to six inches in length. That’s promising for a good crop in a region still whipsawed by a rainy, difficult 2021 and a drought-reduced 2022 harvest.

But then came the night of May 17-18, and a frost that highlights the effects of climate change on wine.

The forecast low of 31 degrees should not have been a threat. But as midnight turned to the early hours of May 18, the mercury dipped steadily to 26 degrees and stayed there for several hours. Cold air slithered down the gentle slopes surrounding the lakes and settled among the vines on lower lands. The breeze across the lakes that normally protects the vines from frost was uncharacteristically still. The few vineyards with frost fans — those unsightly wind machines that stand silent all but a few nights a year — fared pretty well, but other measures, such as burning hay bales to create warmth, proved generally ineffective.

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“A serious widespread spring frost like this is something nobody here can recall ever seeing,” said Hans Walter-Peterson, senior viticulturist with the Cornell University extension in the Finger Lakes.

“We were ready for a potential frost, but we weren’t expecting something like that,” Meagz Goodwin, assistant winemaker at Red Newt Cellars on the east side of Seneca Lake, told me during a recent visit to the Finger Lakes.

“It was a one-two punch, with the warm April followed by the frost,” said John Wagner, owner of Wagner Vineyards, whose family has been making wine near the southern end of Seneca Lake since the 1970s. “We usually get a temperature bump from the lake, but on May 18 … it was very still and the temperature dropped for several hours. That, combined with how far the shoots were out, meant there was regionwide damage. If we hadn’t had the early heat, we might have been able to weather the cold.”

Wagner has been moving his vineyards toward regenerative farming, which includes cover crops between the vine rows to help strengthen the soil and sequester carbon. Interestingly, he said vineyards with that vegetation were hit harder than those farmed conventionally.

“You stop cultivating to save the soil, but you lose that little bit of radiant heat that gives you an advantage during a frost,” he explained.

As consumers, we should remember a few things whenever we read about severe spring frost in wine regions: First, initial reports are always apocalyptic, and it’s difficult to quantify the frost’s effect on the year’s vintage. By mid-June, Walter-Peterson estimated that 40 to 50 percent of the Finger Lakes’ vineyards suffered 50 percent or more damage in their primary shoots. But that doesn’t mean a 50 percent loss of crop, as vines produce secondary shoots when they lose their primaries. (Growers tend to remove secondaries once primaries are safe from frost, to concentrate the vine’s energy.)

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Second, spring frosts complicate planning for the autumn’s harvest, especially when damage is scattered throughout a vineyard rather than uniform. When I was there in mid-June, growers told me the secondary shoots had yet to progress far enough to make a harvest yield projection. So the secondaries will ripen considerably later than the surviving primaries, forcing growers to make some tough decisions. Do they pick the primaries and secondaries separately as they ripen? (Extra time and labor costs.) Or do they leave the primary fruit hanging a little longer while the secondaries catch up? (Always with an eye on potential fall rains.) A prolonged warm, sunny and dry stretch through July and August could make those decisions easier.

At this point, we shouldn’t worry about the smoke from the Canadian wildfires that has been blanketing the eastern United States for weeks. Smoke taint has become a problem in California, Oregon and Australia in recent years, but primarily when fires are close to the vineyards and close to harvest time. If this haze continues, it could conceivably reduce sunlight enough to affect the pace of ripening, but that will be difficult to quantify.

“We won’t really know the full impact of the [frost] until the grapes are picked,” Walter-Peterson said. After rainy vintages in 2018 and 2021 and last year’s drought, he predicted severe events like May 18 will become more frequent. “I know there are at least a few vineyards that will be installing [frost fans] in the next year or two.”

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After a frost like May 18, growers tend to shrug off the initial disappointment and refocus on the task of guiding their vines toward harvest.

“You have to be eternally optimistic to be a farmer,” Wagner said. “There’s always next year.”

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