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News / Northwest

Wine grapes shrivel on the vine in the Walla Walla Valley’s extreme heat

By Emry Dinman, Walla Walla Union-Bulletin
Published: August 7, 2021, 2:26pm

WALLA WALLA — Wine grape yields from the Walla Walla Valley are likely to take a significant hit this year, due to a confluence of extreme weather events at an unfortunate time, according to growers.

Les Collines Vineyard, one of the area’s largest, is expecting around half the yield of an average year, said vineyard manager Brad Sorensen.

“You got some bad years, and you got some good years,” Sorenson said. “This is the year we got.”

Yields were already likely to be low even before the Valley was baked by June’s record heatwave, said Sadie Drury, a grower with North Slope Management and recent recipient of the Winegrape Grower of the Year Award from the Washington Winegrowers Association.

Many vines produced fewer clusters of grapes, she said, likely due to rainy weather from last year.

“Rainy and cloudy weather at bloom time affect the number of clusters formed in next year’s buds,” she explained. “So, rain during 2020 bloom set us up for less fruit in 2021.”

But those shortfalls have been exacerbated by extreme heat.

Grapes can suffer damage in extreme temperatures when they’re exposed to the sun, Drury said.

“Just like human skin, the berries sunburn easily when they aren’t acclimated to high temperatures,” she wrote in an email to the U-B.

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While some sunburn can be tolerable, this summer’s heat had a more dramatic effect on some grapes, said Sorensen of Les Collines.

“There’s different kinds of sunburn,” he said. “You can get the sunburn on the fruit and just get skin damage, but it was so early in the season when those extreme temperatures hit, it shriveled up into nothing.”

But heat’s most visible impact was to make the remaining fruit significantly smaller than normal, Sorensen said, which has contributed to cutting his vineyard’s yearly tonnage in half.

It’s a widespread concern.

Joel Perez, director of viticulture and vineyard manager for Walla Walla Community College, has also seen significantly reduced yields from the estate vineyard he runs.

The college’s Center of Enology and Viticulture produces around 2,300 cases of wine a year, about 60% of which come from grapes grown by Perez and viticulture students.

Grape chemistry may also cause problems for growers, said Perez, who has noticed the estate’s grapes have higher sugars and lower acids than normal.

“High sugars could cause higher alcohol wine, which might necessitate wine makers to add water to their grapes, and it might result in higher taxes,” Perez said.

Grape vines will shut down in high heat and will metabolize organic acids to survive during this period, Perez said, lowering overall acidity. That lower acid could impact the color, stability and taste of the wine the grapes are destined to become, he said.

As harvest season approaches, growers need to be carefully looking at the chemistry of their vines and fruit.

“If acid is a concern for them, maybe they need to pick a little earlier,” Perez said.

Looking ahead

If there is a silver-lining to significantly smaller grapes, it’s that the wine they produce may be proportionately more flavorful, Perez said.

“We will have a greater skin to flesh ratio, which could potentially lead to greater color and other flavor compounds,” Perez said.

“But in order to make the best decisions, growers should be paying attention to the grape chemistry in this very awkward year,” he added.

Even if wine quality from this year’s vintage is of a premium quality, Perez worries about the financial impact that reduced yields will have on growers.

“So there has to be a balance in communication between the wineries and the vineyards on the money that is being exchanged,” Perez said. “If the grower’s putting out the same effort, but regardless of their effort they have a lower yield, they’re the ones losing out on the money.”

But for most growers, renegotiating prices isn’t likely to happen, Sorensen said.

“Prices were set when we send out contracts,” he said. “We don’t get to play with that that too much. Ultimately, we just want to grow the highest quality crop we can and hope for a better year.