Northern California’s harvest was already winding down when the wildfires tore through parts of Sonoma, Napa and Mendocino Counties, forcing winemakers and residents to flee. With fire crews still battling the flames, and many areas under mandatory evacuation, winemakers are facing challenges as they try to finish what had once looked to be a relatively easy harvest.
By the time the fires arrived, vintners had harvested the majority of their grapes. Karissa Kruse, president of the Sonoma County Winegrowers, estimates that 90 percent of the region’s winegrapes had been picked. The Napa Valley Vintners reported the same figure, while the Mendocino WineGrowers estimates that most of the white grapes and 75 percent of the region’s red grapes were in.
“The 2017 vintage has been a hot and dry one, but we are very pleased with the quality of the wines in tank right now,” said Remi Cohen of Lede Family Wines in Stags Leap District, a Napa appellation in the Atlas fire zone. “The grapes were acclimated to heat early in the season this year, had developed thick skins, and we were able to harvest most of our crop at relatively low Brix despite the heat.”
That allowed an early harvest. But vintners report that there is still some Cabernet Sauvignon and other late-ripening grapes hanging on the vines. Now they are scrambling to pick the last of their grapes and ferment the wines while coping with evacuations, power losses, road closures and thick clouds of smoke.
There is a good chance the vines survived, even if their grapes have not. “During the movement of these fires, the vineyards have actually served as a fire break in many instances and saved nearby homes and structures,” said Cohen. She believes the vines' green foliage and the mowed cover crops in the vineyards helped slow or halt the flames—green vegetation is harder to burn than the fires’ typical fuel, the dry scrub on the ground in the hillside forests of oak and pine.
Dr. Anita Oberholster, cooperative extension specialist in enology at the University of California at Davis, agrees that many of the vines should be fine since they are hard to burn and the strong winds actually helped to blow the fires through the vineyards very quickly. “We really think the impact on the vines will be minimal,” she said. “If there is an impact it may be that the buds have burned off and there may be an impact on the yields next year.”
Those who have been able to pick their grapes are facing other challenges. Pickers and winery staff have had to evacuate, and some have lost their homes. “We are running on minimal crews right now,” said Philippe Melka, who consults for more than a dozen labels and produces his own wines.
Power outages are also creating issues for the wines fermenting in tanks. Adam Lee of Siduri says his winery in Santa Rosa survived, but it didn’t have power. On Tuesday, parent company Jackson Family Wines provided a generator. “We started out by going through the ferments,” Lee said. “It had gone a couple days without punch-downs and temperature control.”
Most winemakers try to keep their red wine fermentations between 70° to 85° F and white wines between 45° to 60° F. If the temperature gets too hot, the wines can taste cooked or the yeast can die before completing fermentation.
Lee put dry ice of top of some of his mid-ferment wines and inoculated others. He says that without power, there are ways to siphon out bins and tanks, but you can’t press the skins, and may lose up to 25 percent of the wine. “I think everything is going to be OK,” he said. “I think we are going to make fine wine out of it.”
Jesse Katz, who makes his wines at Envy in Calistoga, says he had crews spend the night there so they could still ferment, but lost power Thursday. “Today I brought Oliver Ranch [Cabernet] to Bevan Cellars because they wouldn’t let us into Calistoga.” The town has been under a mandatory evacuation order.
Besides being a health hazard, the thick smoke has some vintners alarmed. “We are obviously extremely concerned about smoke taint” impacting grapes still on the vine and fermenting wines, said Melka. He is taking steps in the vineyards and cellars to minimize contact with the smoke since compounds in the smoke can be absorbed through the grape skins, imparting a distinct smoky note in the wine.
Smoke residue contains high concentrations of volatile phenols, such as guaiacol and eugenol, which can accumulate in grape skins. They're released into the wines during fermentation.
Melka says he is sending samples to ETS Laboratories, the leading diagnostician for California wineries, but that the company is currently overwhelmed. He estimates that 15 percent of his grapes still need to be harvested and is evaluating each vineyard individually and notifying his clients of the risk.
Oberholster says while smoke taint is a risk, it's difficult to predict, and the compounds that cause it only become problematic at high levels. “I’m not all that worried about wines that are already made or fermenting,” she said, noting that the carbon dioxide, a byproduct of fermentation, will help protect the wines. But like so much in Northern California wine country right now, the future is unknown.