Home Viticulture Fire & Ice: Can Pruning Practices Mitigate Effects of Climate Change?

Fire & Ice: Can Pruning Practices Mitigate Effects of Climate Change?

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As scientists and legislators search for large-scale solutions to extreme weather patterns, wine-growers are look for short-term fixes that they hope will help increase their shot at a successful harvest. For many, that means changing pruning practices.

Kathleen Willcox

Climate change is transforming wine-growing. Grapes are one of the most weather-sensitive crops on the planet, and since 1880, the average global temperature on Earth has increased more than 2 degrees, with two-thirds of that warming occurring since 1975.

Pruning for Frost

Increased temperatures may mean earlier ripening, but the warming isn’t consistent. Last year, Spring frosts incurred more than $2 billion in cost to the French wine industry for damage to budding vines, according to estimates.

Vineyard frost in Bordeaux / iStock
Vineyard frost in Bordeaux / iStock

Here in the States, Joe Nielsen, director of winemaking at Ram’s Gate in Sonoma, has been experimenting with pruning time changes since he joined the 28-acre estate in 2018.

“I do subscribe to the notion that pruning affects the physiological phase within the grapevine, though only by a few days,” he says. However, “As with many things in grape-growing, it’s hard to have great evidence of anything working after just one year. Case in point: I was under the impression that our location never experiences frost, but in 2020 we did, and I lost 15 to 20 percent of my crop.”

He thought he learned his lesson and pruned “really early” in 2021 to avoid another frost incident—but ended up delaying his bud break. So now he wonders, because the spring season was so dry, did he manipulate his vines to miss the available soil moisture during the early growing season?

This year, he plans to time pruning in the middle of the two extremes, and while he admits it’s “a lot educated guessing” on what that proper timing of pruning will be, he still says he believes that pruning strategically is both possible, and advantageous.

Bud break at Ram's Gate / Courtesy Ram's Gate Winery
Bud break at Ram’s Gate / Courtesy Ram’s Gate Winery

At Cliff Lede Vineyards in Napa, director of vineyard operations Allison Wilson says they prioritize pruning as the single most important activity in the vineyard. “We consider pruning an art, and we are pruning for the current and future vintages with each cut,” she says.

When pruning is done with care, Wilson explains, it encourages the growth of wood in areas where it will be needed in future vintages. The goal of pruning for the future is of separating spurs that are clustered too closely, and filling in blanks where there has been die-back. Tactical pruning also serves as a secondary insurance policy in the event of frost, when primary buds perish and secondary buds—with luck—sprout.

Wilson pre-prunes each block to prevent frost damage, but admits “there is a small window” to make an impact that could save a vine from frost, and adds, “we are always at the will of mother nature.”

Pruning for Fire & Heat

Wildfires, which are linked to climate change, cost the California wine industry $3.7 billion in 2020 alone, according to industry analysts.

Reducing the chance of smoke and fire exposure has transformed pruning practices at Hamel Family Wines in Sonoma.

Winegrowing director John Hamel says that pruning just a few days early lowers the chance of exposure, and also helps guard against “late season heat spikes with low relative humidity levels, which are becoming more frequent and extreme.”

Hamel dry-farms their vineyards in a bid to create ultra-concentrated, higher-quality wines. But extreme heat spikes threaten the hard-won progress by driving up sugar levels and throwing off the acid balance—sometimes in a matter of a few days.

Glass fire captured in Calistoga California (Napa Valley)
Glass Fire captured in Calistoga, California /iStock

Matt Dees, winemaker at Jonata and The Hilt Estate, in the Sta. Rita Hills considers exposure to heat one of his biggest environmental threats as well.

Like Hamel, Dees’ main concern is fruit quality. “Some people are picking Syrah in Sta. Rita Hills in December—that is not a good look moving forward,” he says, explaining that the longer hang-time is more beneficial in cooler conditions, where the grape can ripen slowly and maintain a balanced acid-sugar balance. 

“It’s unclear, though, how much you can shift harvest dates by earlier pruning,” he adds. Whenever he’s tried he’s observed that the vine seems to catch up, and the harvest date isn’t improved enough to make a significant difference. “But we still see early pruning as part of our intentional farming process.”

Not Adjusting Pruning

But not everyone is ready to change their pruning practices.

“Ripening needs to occur in the appropriate season, irrespective of events such as wildfires,” says Chris Howell, general manager of Cain Vineyard & Winery in Spring Mountain District, who saw firsthand the effects of wildfires when the 2020 Glass Fire destroyed the winery, heritage barn and houses on the property; some of the vines were also completely destroyed.

“Timing” bud break according to concerns about frost and wildfires not only doesn’t work, arresting or encouraging ripening off of mother nature’s timetable could endanger the quality of the wine, according to Howell.

Others also try to follow the land’s lead.

At Gamble Family Vineyards, with 175 acres across Napa, director of viticulture Raymond Reyes, is also concerned about pruning. He agrees that “timing can affect bud break and critical vine-growing stages” and with the notion that pruning may be able to avoid wildfires, but doesn’t take these factors into consideration himself. Instead, Reyes bases his pruning decisions on the growing season’s weather patterns and how best to achieve optimal phenolic ripeness. 

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Kathleen Willcox

Kathleen Willcox

Kathleen Willcox writes about wine, food and culture from her home in Saratoga Springs, N.Y. She is keenly interested in sustainability issues, and the business of making ethical drinks and food. Her work appears regularly in Wine SearcherWine Enthusiast, Liquor.com and many other publications. Kathleen also co-authored a book called Hudson Valley Wine: A History of Taste & Terroir, which was published in 2017. Follow her wine explorations on Instagram at @kathleenwillcox

 
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