Torrid Temperatures Shrivel California Wine Grapes To Raisins

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Humans weren’t the only ones caught off guard and uncomfortable by the Bay Area’s Labor Day weekend heat spike.

Wine grapes, unaccustomed to those temperatures at this time of year, were left shriveling on the vines, in many cases dehydrated by excessive daytime temperatures that weren’t cooling down enough at night. The heat episode has turned what was looking, just last week, to be a promising and average-yielding vintage into a year that looks more uncertain, in both quality and quantity.

“I’ve been making wine for 34 years, and I don’t think Napa’s ever seen this excessive heat at this stage of ripeness,” said Pam Starr, co-owner of Crocker & Starr Wines in St. Helena, where temperatures exceeded 110 degrees three days in a row. “I thought we were going to make it through without a lot of repercussions, but that’s not the case.”

The repercussions, mainly, are raisins. Water evaporates from berries under high heat. Some vines’ entire metabolic process may shut down. Irrigation can help prevent or counteract dehydration to some degree, but many winemakers try to avoid irrigating too close to harvesting dates, for fear of diluting the berries’ flavors.

With irrigation, Starr was able to resuscitate some of her parched fruit. But as she walked through her estate vineyard this week, she estimated some blocks to have lost as much as 50 percent of their crop due to raisining.

Crocker & Starr produces Bordeaux varieties. Starr harvested her Sauvignon Blanc in mid-August, and says it tastes delicious. But red grapes like Cabernet Sauvignon in Napa typically need until at least mid-September to reach full physiological ripeness.

For Napa Cabernet, the heat spike came close to the point of ripeness — but not close enough. Although September heat waves are not uncommon for California wine regions, one this early in September is nearly unprecedented. When there have been heat waves, in warm years like 2004 and 1997, they came a couple of weeks later than this year’s. In those cases, it was an easy call to pick the grapes, which were further along in their development, just before the temperatures rose.

Pinot Noir, which ripens earlier than Cabernet Sauvignon, was closer to ripeness in many California vineyards when the heat hit. Many Pinot makers all over the state rushed to get the grapes off the vine last weekend before the clusters all turned to raisins.

“The extensiveness of the dehydration was something I’ve never seen before,” said Jasmine Hirsch, of Hirsch Vineyards in Cazadero, which grows Pinot Noir and Chardonnay. “It’s exceeded 104 degrees here before, but never during harvest.”

From what they’ve picked so far, Hirsch winemaker Anthony Filiberti estimated that the site’s yields are down about 10 percent due to raisining, and another 10 percent due to water evaporation, which affects grapes’ weight.

Plus, Hirsch expects to have to declassify some wines this vintage — wines that, because they may taste raisiny and overripe, will not make the cut. That could mean putting grapes destined for a vineyard-designate or block-designate wine into a less expensive blend.

In the Santa Cruz Mountains, Thomas Fogarty Winery expects a similar fate for some of its Pinot vines. When the heat hit last weekend, proprietor Thomas Fogarty Jr. and winemaker Nathan Kandler found themselves irrigating some of their vineyards, something they haven’t done since 2009. That saved many of their vines from dehydration, Fogarty reported, but not all: “Even with water, the end vines (which get the most direct sunlight) in Windy Hill Vineyard showed some ‘saggy berry syndrome,’ and those clusters were picked and kept separate.” The wine from those vines, Fogarty added, will likely go into their cheaper appellation blend, or be “tossed.”

Vineyard labor already was tough to secure, and the heat spike exacerbated it. When grapes are ripening in such a compact time frame, and everyone wants to harvest at once, it’s always more difficult to find the hands to pick the fruit. “My phone was blowing up with requests from other vineyards needing pickers ASAP,” Fogarty said.

“Whenever it’s this compact, it’s always more stressful, especially for our vineyard crews,” said Hirsch. “Everything getting ripe at once means you have bigger days.”

Grapes that were harvested before the heat spike, already on their way to becoming wine, are looking beautiful, vintners report. Many wines unharvested yet may turn out fine. A lot depends on sorting out the raisins before the berries get to the fermenter, said Pam Starr.

“On the face of a cluster, the best we can hope for is that they become dry raisins,” Starr said. “We can sort that at the machine pretty easily.” She’s more concerned about the stealth raisins — grapes that might be moderately raisined, or slightly overripe, but with less overt visual markers.

“Sorting and capturing delicious fruit — that’s the goal,” Starr said, “and letting the raisins go into cereal boxes.”

By Esther Mobley
September 11, 2017
Source: Sfchronicle.com