'Early' Doesn't Equal 'Better' in Vineyards

Premature bud break brings fear to grapegrowers

by Jane Firstenfeld
wine vineyard bud break carneros ava
Buds on a grapevine leaf out this month in the Carneros appellation. Photo by Brittany Pederson of Renteria Vineyard Management for Napa Valley Grapegrowers

Bay Area, Calif.—The Feb. 15 announcement that grapevines had broken bud in southern Napa County might have seemed like a boast to non-farmers. In fact, it sounded an alarm not just in Napa but throughout Northern California vineyards.

After a record dry and relatively warm winter dormant season, the early bud break—followed by persistent sub-freezing temperatures—forced some grapegrowers to switch from passive to active frost-control measures.

“Passive” control calls for delayed pruning. The “active” version requires use of devices including wind machines and sprinkler systems, which both have noted drawbacks: They are expensive and must be installed prior to frost danger. Wind machines can be noisy, and sprinkler systems can draw negative attention, as they did in Sonoma County in the early years of the recent historic drought.

Bud break still scarce
Garrett Buckland is president of Napa Valley Grapegrowers and owner of Premiere Viticulture Services, which manages more than 2,000 acres of vineyards for 22 Napa Valley properties. He estimated that only 2% to 5% of Napa vineyards had experienced early bud break—mostly in the more temperate, southern Carneros district, which is known for its Chardonnay and Pinot Noir grapes.

In Northern California, freeze conditions can menace vines until June, Buckland said. He reported seeing snow on the east side of Napa Valley during the Presidents Day weekend. “We’ll be worried until April,” he added.

The most common active frost protection is the use of overhead or micro-sprinklers. Despite what non-farming residents may fear, these systems do not require great amounts of water. “They are recycling and set up to have drainage that refills ponds. We can use the same drop of water seven or eight times,” he said. In Carneros, Buckland said he’d observed icicles on vines where sprinkling is used.

He explained that there are two different types of frost. Radiation frosts are standard in spring, and for these, the active anti-frost tools can be 100% effective. But hard freezes are potentially more damaging and can cost growers an entire year’s harvest. Hard freezes are much more common in northern climates including Oregon and Washington. Neither necessarily kills the vines, however.

“Normally we are still dormant; buds are tight. There’s still a lot of season yet,” Buckland observed with typical farmers’ optimism. He believes that last year’s rainfall was sufficient to revive the soil profile and is hoping for another dose in March.

Other counties weigh in
“Early is not better,” stated Jonathan Walters, director of farming for 30,000-case Brassfield Estate Winery in Lake County, which farms 270 vineyard acres in the High Valley AVA.

On Feb. 6, he reported that he’d checked all of the typically early blocks for bud break, and all remained “nice and tight. Let’s hope it stays that way for another six to eight weeks,” he said

As of Feb. 16, he still observed no bud break, including normally early varieties like Grenache and Pinot Noir. Walters said he estimates possible bud break by watching the local peach trees, which are showing some bud swelling. So, he said, grape bud break may be 10-12 days earlier than normal this year.

From the Livermore Valley AVA in San Francisco’s East Bay, Dan Baldwin, general manager and senior winemaker at 4,000-case Rios-Lovell Winery, said earlier this month, “Typically bud break occurs closer to early or mid-March, when the average daily temperature is 50º F. Although the temperature has been close to that average these past few weeks, there is a certain number of hours of daylight also required to prevent bud break from occurring way before the likelihood of frost damage will kill all the new buds on the cane. Nature is pretty good at protecting herself.”

On Feb. 16, Lisa Maier, owner of 3,000-case Las Positas Vineyard, reported, “With the cold weather, nothing is pushing yet. This is good news; I’d be really worried about frost damage. There’s still some minor risk, but our vines are still fairly well protected. You can only control so much.”


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