kushman on wine
Frost wars in wine country.
WRITTEN BY RICK KUSHMAN
ILLUSTRATION BY PAUL KREIZENBECK
Ah, spring in wine country. Vines and flowers are awakening and the world becomes filled with possibility. But there’s also a bitter, brutal war against frost.
Even in the mildest years, frost wars are constant. The battles start early in clear, cold mornings — at 3 or 4 a.m., when the temperatures bottom out. That’s when frost alarms can ring across Northern California wine country.
They sound everywhere — in Napa, Sonoma, Lodi, Monterey. Name your region. But the greatest problems are in the central Sierra foothills, Nevada and Placer counties, down through El Dorado, Amador, Calaveras, and more.
Frost battles are common for all farmers. The California Farm Bureau Federation gives warnings throughout the state in spring. But wine country is especially vulnerable.
For vineyard managers, mid-spring is the dangerous stretch. In the foothills, nights can drop into the 20s, but the warm days trigger the vines to sprout leaves. (That’s called bud break.) Dormant vines in January or February handle ice and snow just fine, but frost will kill young buds. Vines will sprout more buds, but the volume and quality of the finished grapes drop enormously.
So when the frost alarms sound and vineyard managers are forced from their beds to battle, what weapons do they use? Almost all seem odd.
Smudge pots are an old favorite. They look like large backyard heaters that put out both warmth and thick smoke layers that hold in heat. But they’re increasingly unpopular because, rather obviously, no one is thrilled about thick smoke layers.
Probably most common are giant fans, some more than 30 feet tall, some squat and fat. They work in two ways. First, air flow helps prevent frost, which is why there’s less frost on windy nights. Second, cold air sinks, meaning toward the ground, and the vines get the worst of the cold. Fans help bring slightly warmer air down to vine level.
Then there is the seemingly logic-defying weapon: sprinklers. Spraying water to form ice on vines actually keeps them warm. Or warm enough. In very simple terms, when water changes to ice, that change creates a bit of heat. It’s just enough to keep the vines above 32 degrees. Sprinklers keep vines safe down to 28 degrees or so, but, also obviously, the method requires a decent amount of water.
Good bar bet: Name the month in which vineyards use the most water. People will guess sometime in summer. But, nope. In the foothills, it’s April.
Many of the smaller vineyard owners rely on simple physics for help. Because cold air sinks, it flows down hillsides just like water. Vineyards planted on hillsides allow air to roll downhill to outlets beyond the vines, making them less vulnerable. This is why some vineyards mow the grass between rows — to help the flow.
“People’s idyllic image of winemakers is us riding through vineyards on a white horse,” Greg Boeger, founder of Boeger Vineyards in El Dorado County, once told me. “In spring, I’m riding through half the county in my truck at 4 a.m. trying to figure out what fans to turn on.”