Harvest pressures rise with the extreme heat in Sonoma County

Shriveled grapes, sunburned berries and excessively high brix, or measure of grape sugar, are the telltale signs of a harvest season heat wave, which is forecast for Sonoma County through Thursday.

With temperatures expected to climb into the triple digits over the next few days, many local winemakers are scrambling to harvest grapes as quickly as possible to avoid potential heat and sun damage.

“Most of our winemakers are trying to bring in Russian River pinot noir as fast as possible,” said Ronald Du Preez, general manager and partner at Sugarloaf Crush, a custom-crush facility in Santa Rosa.

“We had five trucks of fruit lined up this morning at 7 a.m., so we’ve been processing grapes like crazy. Our other clients in Philo and Anderson Valley aren’t quite ready to pick, but this week’s heat wave will push things right along. We expect next week will be very, very busy.”

The rush to harvest grapes has Sugarloaf processing them as promptly as possible. The crush facility is operating at full capacity for 16 hours a day, and Du Preez said Sugarloaf will crush nearly 50% of this harvest’s fruit by the end of next week. That’s about two weeks ahead of an average year.

Despite the damaging frost that occurred during bloom this spring — which is expected to reduce grape yields across the North Bay — the 2022 growing season has been fairly uneventful, with mild to moderately warm temperatures so far.

“Early bud break and bloom resulted in one of the earliest harvests on record,” said Karissa Kruse, president of the Sonoma County Winegrape Commission. “Depending on the grape variety and area of the county, we’re about 20 to 25% through harvest, which is about two weeks early, compared to a ‘normal’ year. The impending heat wave will expedite ripening, and harvest will continue at a fast pace.”

At Rodney Strong Vineyards in the Russian River Valley, winemaker Greg Morthole is concerned the extended heat wave and low humidity will lead to damaged fruit in the vineyard.

“The juice inside a growing pinot noir grape is 15 degrees warmer than the ambient air temperature,” Morthole said. “When it’s 95 degrees outside, the grapevine shuts down and stops ripening. That’s when you get shriveled, unripe fruit.”

While Rodney Strong already has picked most of its chardonnay, the majority of its sauvignon blanc and a significant portion of pinot noir are still on the vine.

“Pinot noir ripens like a rocket ship, so this heat isn’t good for quality,” Morthole said. “We’ve already picked our higher-tier pinot noir, so it’s our middle-tier fruit that is going to have to weather this heat.”

In Dry Creek Valley, Jim Ricci, who has been farming in Sonoma County for 32 years, believes “the grapevines will weather this heat just fine.

“The warm temperatures may reduce tonnage further, but I still think it has the potential to be a beautiful vintage,” he said. “Our main concern is water. The weather has been really temperate this year, and we haven’t had any major heat spikes. So there has been less need for irrigation. We’re on a well, so we try to be very judicious with water. But the vines are really going to need water in this intense heat.”

Christian Klier, a North Coast grape broker with Turrentine Brokerage, agrees the high temperatures could be a significant issue in water-restricted zones like the Russian River Valley.

“It’s late in the season, so water reservoirs and wells are really low,” he said. “That’s not going to be good for the fruit. People are really concerned.”

White grapes like chardonnay, sauvignon blanc and pinot gris are likely to be most impacted by the high heat according to Klier, as well as early ripening red varieties like pinot noir and merlot.

“Many wineries are rushing to pick because of the heat, so tank space is becoming a problem,” Klier said. “If production is stalled at the wineries, we could see a lot of disappointed farmers without crushed fruit.”

In the end, whether to pick or let fruit continue to hang on the vine during a heat wave is an educated guessing game, according to winemaker Adam Lee of Clarice Wine Co. in Windsor.

“Picking before the heat is undoubtedly the safer choice. Waiting and watering until after the heat is much more risky,” he said. “What if the forecast is wrong and the highs are higher than expected, or the duration of the heat is longer than forecast? Will I be right or wrong? I don’t know yet. But it’s all on the line, and we shall see.”

You can reach Staff Writer Sarah Doyle at 707-521-5478 or sarah.doyle@pressdemocrat.com.