Spring Frost Could Limit Vine Yields This Fall

     Some winegrape growers are calling this spring the frostiest in years, with scattered reports from many of California’s North Coast appellations of close calls and some damage to vine shoots that had budded early.

     The temperature around the North Coast dropped to around freezing on up to 13 nights in late March and early April, forcing growers to lose sleep as they wielded or readied frost-protection measures such as water sprinklers and wind machines for sometimes four or five nights in a row.

     Early projections for how much frost damage will affect winegrape crop yield this season range from 5 to 10 percent. Yet the full extent won’t be known until grape clusters start forming and any secondary or tertiary vine growth appears after any frost-burned initial shoots die.

     Jeffrey Popick, a vintner in St. Helena who represents more than 100 North Coast growers for the Allied Grape Growers marketing group, told the North Coast Business Journal that he has seen and heard about frost damage in the Carneros appellation and in Suisun Valley of Solano County, locations where three- to four-inch Chardonnay shoots show signs of burn. “It’s not widespread, but it’s enough to add up to something,” he said.

     Wild swings of cold and warm spells in the past several weeks are courtesy of four cold-air and high-pressure systems from western Canada that were too dry to allow clouds to form a nighttime blanket, according to Popick, who writes a local newspaper weather column.

     The lowest temperature reported in Sonoma County was 25 degrees, and it reached 27 degrees for three hours in Russian River Valley, according to Nick Frey, President of the Sonoma County Winegrape Commission.

     “That kind of temperature puts a lot of stress on frost-protection systems,” Frey said. “I haven’t heard of anyone running out of water, but it taxed those with storage from winter diversions” from streams or rivers.

     Charlie Barra of Redwood Valley Vineyards in northern Mendocino County said he used up a lot of the water in his storage ponds battling 15 nights of frost since March 16. “We’re hoping we will have a little rain water to fill them up,” Barra said.

     Running out of water is a real concern. In 1973, Napa Valley growers used up all their frost-protection water after a dozen straight days of frost and lost a large portion of the crop on the 13th night. In the late 1980s, the Potter and Redwood valleys of Mendocino were hit with 23 straight days of frost, and growers there nearly ran out of diesel for the wind machines and sprinkler pumps and water to spray, recalled Ed Berry Jr. of Cononiah Vineyard.

     Guinness McFadden, who has been farming 160 acres of mostly white varieties of winegrapes in Potter Valley since 1970, said he has burned several thousand gallons of red diesel at $3.85 a gallon running sprinkler pumps during 20 nights of frost, including 14 straight. Last year, only a few nights had worrisome temperatures.

Posted in Wine Region Profiles
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