In what some are calling the worst frosts since the early 1970s, a bitter spring cold snap has damaged California vineyards throughout the state. As temperatures dipped into the low 20s throughout the state, growers scrambled to protect tender buds with sprinklers, wind machines, heaters and other frost protection methods. While these measures decreased the amount of harm done when they could be used, there was significant damage where frost protection methods were ineffective or unavailable.

According to Jennifer Kopp, executive director of Napa Valley Grapegrowers, 2008 has been an unusually bad frost season. "If you talk to most people, they are going to remember this year as a historic frost season," she said. "This frost affected some people who have never had to protect for frost before so they didn't have anything on-site. We're hearing this was the worst since 1973," said Kopp.

The cold snap affected vineyards from around the state, with reports of damage from Mendocino, Lake, Sonoma and Napa counties, as well as vineyards in Lodi, Paso Robles and elsewhere on the Central Coast. Growers who suffered a significant amount of bud loss are left to hope for strong secondary bud growth from their damaged vines.

Frey indicated that most Sonoma County regions had at least some damage, though at press time the extent of the damage cannot be determined. "There's no estimate yet and any guess before flowering and fruit set is just a guess," said Nick Frey, president of the Sonoma County Winegrape Commission. "You can likely guess frosted shoots will produce half a crop at best. If secondary buds are not fruitful, then that shoot will have zero yield. Then it is a question of how the unaffected shoots yield. The next critical period will be weather during flowering.

"The areas that are worst off are where they never experienced frost until this year," continued Frey. "Those had no protection and therefore experienced damage. Most people with sprinklers for frost protection came through well. Some possible exceptions are growers whose micro-sprinklers froze due to the very low dew points or if reservoirs ran out of water. Wind machines were not effective in every instance, especially areas where dew points were low and temperatures got too cold."

There was widespread damage throughout Napa's growing regions, but the severity was largely site-specific "There's a range of damage. Some people are saying there's one or two plants affected, while there are others who have five acres that were left without a leaf," said Kopp. "We're working under the assumption right now that we're going to see something between 10 to 30 percent loss. Some of the places that look damaged now may be able to rebound."

Lake and Mendocino counties appeared to be the hardest-hit, with some growers losing
nearly all of their first growth buds. "I'm in Anderson Valley, at 1,200 feet, and we lost 70 percent of our Pinot Noir and 90 percent of Pinot Gris," said Fred Buonanno, owner of Philo Ridge Vineyards. "I've heard others in the county have lost varying amounts. The frost seemed to do a little more damage up high because the dew point dropped precipitously and with the wind there was no moisture in the air."

Buonanno reported that he knows of growers elsewhere in the county who lost up to 80 percent of their bud growth, though some other areas came through the cold snap relatively unscathed.

Others are optimistic about Mendocino's 2008 season forecast. "We are projecting an overall increase in quality as a direct result of lower yields from stressed vines. This corresponds directly to a possible loss of as much as 30 percent of the Mendocino County winegrape crop at harvest this year. We anticipate much higher than average prices for the uncontracted fruit that remains on the market," said Paige Poulos of Paige Poulos Communications, official spokesperson for the Mendocino Winegrape & Wine Commission.

Some areas of Lodi also took a heavy hit from the cold. "Lodi suffered serious damage on the outskirts of the district, up on the Borden Ranch and Clements Hills areas, where damage was as high as 60, 80 and 100 percent. Also to the west in the Delta there were instances of near wipeouts," said Mark Chandler, executive director of the Lodi-Woodbridge Winegrape Commission. "I estimate 15 to 20 percent crop loss for the region. White varieties were harder hit than reds, as they are farther along in their development. The core Lodi area was lightly affected, just a few leaves here and there, but not serious damage."

Because frost is unusual for the region, many growers do not have frost protection tools like sprinklers or wind machines installed at their vineyards. Chandler said growers using furrow or drip irrigation were able to mitigate the damage somewhat, but the help was sometimes dependent on vineyard practices applied before frost was a concern. Also, growers with cover crops, even if they had been recently mowed, "fared much worse than those which had been recently plowed and had a clean floor," said Chandler.

Using sprinklers was a dicey proposition for growers in some areas where rainfall has been scarce. Growers had to determine if they would use their limited water resources to protect the vines from the frost, which would likely leave them without enough water to last through the growing season.

"I am sure there are people with reservoirs for irrigation that used most, if not all, their irrigation water keeping the shoots healthy," said Frey. "They probably have a full soil profile for the vines, but some may be dry farming the rest of the year. People with wells are not affected, but those who catch winter rainfall in reservoirs have concerns."

Stacie Jacob, executive director of the Paso Robles Vintners and Growers Association reported that there were some vineyards that were damaged by the cold weather. "The diversity of the AVA with its various microclimates was evident as frost damage was spotty in low areas across the more mountainous regions and more evident other areas, specifically in the Estrella Road, Creston and Shandon regions. The overall shortage will impact the market as the frost will reduce the unsold grape supply."

Jacob said that the extent of the damage is still being quantified. As in other regions, growers who were unable to use frost protection suffered the most damage.

Dave Michul, vice president, viticultural and vineyard operations at Beckstoffer Vineyards, said that damage was dependant on the level of frost protection vineyards were able to employ. "We have a vineyard in St. Helena where we didn't have frost protection, so we had some damage there," said Michul. "We're still assessing how much. It's not really bad, it's maybe less than 10 percent. But we've never had frost at this location before, which is why we didn't have frost protection there."

Michul indicated that the majority of the company's vineyards, located throughout the North Coast, have frost protection. In addition to Napa, some unprotected properties in Mendocino and Lake counties were damaged, though not severely. He indicated that the temperatures in their Lake County vineyards were colder than anywhere else they farm.

--Mary-Colleen Tinney