Frost damages wine grape crops in SLO County

Overnight frosts that occurred in the early-morning hours April 9 and 10 caused widespread damage to North County vineyards, and the losses may meet state qualifications to be deemed a disaster.

“It was a hell of a frost is what it was,” said Dana Merrill, owner of Mesa Vineyard Management and Pomar Junction winery. It was the coldest and most widespread freeze he’s seen in 25 years, he said, citing frost as far as King City.

The tender tissues of buds are just forming and breaking open at this time of year, especially on white grapes and Rhône varietals such as vio-gnier and grenache, he said.

“The vines were just waking up from winter, and Mother Nature came and zapped them,” said Stacy Jacob, executive director of the Paso Robles Wine Country Alliance.

How the production of wine grapes — the county’s top crop at $173.5 million in 2010 — will be affected is difficult to gauge at this point, as microclimates vary. The Tribune interviewed several growers and a wine industry expert, all of whom categorized the event as severe and widespread.

Agricultural Commissioner Marty Settevendemie said crop losses will likely meet the 30 percent threshold for Gov. Jerry Brown to declare a disaster.

If so, growers will be eligible for federal assistance to offset losses. The San Luis Obispo County Agricultural Department is assisting them by compiling reports of the damage.

The San Luis Obispo County Viticultural Area is 30,000 acres, 26,000 of which fall between Cuesta Grade and the Monterey County line. There are more than 100 independent grape growers, some of whom also operate wineries.

According to Jacob, who surveyed a dozen North County growers, none were spared.

Merrill said he may have lost 30 percent to 60 percent of buds on the 6,000 acres he grows across the Paso Robles region. The 300-acre crop that Lowell Zelinski manages for Precision Ag Consultants may have seen losses of 50 to 75 percent, he estimates.

Long, cold nights

As temperatures dipped into the mid-20s across the North County for several hours each night, growers stayed awake to respond with standard frost-prevention measures, including wind machines to flush warmer air from above to circulate around the vines. But “there was no warm air to pull from,” Merrill said. “It was the kind of cold you’d expect in January — but the grapes are asleep then.”

Some of Merrill'’s viognier emerged from the untimely frost “fried like you took a blowtorch to them,” he said.

Those who employed overhead sprinklers fared better, but crop losses were still widespread, as frost reached higher hills and elevations where growers would not normally encounter frost.

Some damage was also reported from a hail storm April 8.

Edna Valley and South County vineyards appear to have escaped the worst of the freezing. George Donati, general manager of Pacific Vineyard Co., estimated less than 2 percent damage on his 2,000 acres of crops in Edna Valley near San Luis Obispo, as temperatures dropped to a low of 29 degrees the night of April 9. The ground, soaked from previous rains, helped prevent further damage, Donati said, though he added, “We were just lucky.”

Second chances

Luckily for growers, frostbitten vines aren’t dead.

“The grape is a resilient creature. It has backup plans,” Merrill said.

Even if primary buds were bitten by the cold, grape vines still produce secondary and even tertiary buds.

The yield for secondary buds is less fruitful than for primary buds, but some growers say the fruit is of higher quality.

For farmers, frostbitten vines still need as much attention, if not more, than normal vines. “You can’t just stop farming them,” said Zelinski, because the vines are forming the cells to make next year’s crop.

Growers are relishing this week’s warmer temperatures, Jacob said, which will wake up the vines and accelerate growth.

Merrill is curious to see if the primary buds of his merlot and cabernet grapes will still emerge. “It was so darn cold, they got cooked before they opened. What will come out of those?”

A delayed growing season means harvest will likely be delayed from early to late October. Unfortunately, that means growers could encounter frost again at that time, Zelinski said.

But for now, the growers will tend to their crops and wait for secondary buds to bloom.

“A frost of this magnitude reminds us that wine is about farming,” Jacob said.

NOTE: The fifth paragraph of the story was corrected to reflect that San Luis Obispo County's wine crop was valued at $173.5 million in 2010. The seventh paragraph was corrected to reflect that growers could be eligible for federal, not state, assistance. References to Dana Merrill were corrected to reflect his correct surname.