Late spring frost threatens vineyards in Oregon and California

Grape growers and grape growers in Oregon assess the damage after a severe late frost hit the Willamette Valley in recent days. The week of April 10 saw record high temperatures – up to 26°F in some areas – just as vineyards were beginning to bud. Frost is not uncommon in Oregon, but it usually hits earlier in the season when the vines are still dormant. “We have never seen such cold temperatures so late in the season,” said winemaker Josh Bergström. wine spectator.

Winemaker Roco Rollin Soles echoed that sentiment. “I’ve never seen spring frost damage on our hillside vines before, and I’ve never seen snow in the Coast Range in mid-April,” he said.

The impact of frost varies from region to region and even from vineyard to vineyard, depending on altitude and other factors. “I understand that the vineyards of Eola-Amity Hills seem to have held up better than areas such as Chehalem Mountains and Yamhill-Carlton,” said Lavinea winemaker Isabelle Meunier.

The extent of the damage will not be clear until daytime temperatures in the valley reach 70°F for several days, which would restart vine growth and reveal which buds are still growing and which have been damaged. Temperatures this week are not expected to exceed 60°F.

“The young vines had developed an inch or two of growth, while the mature vines were just starting to bud,” said winemaker Ken Wright. “The exposed green tissue of young vines was extensively damaged at all of our sites.” Chardonnay vines were generally further along in development than Pinot Noir and could suffer significant crop loss. “After cutting out hundreds of buds in all places [to check for damage]my instinct is that the damage to the primary buds is significant and there is also damage to the secondary buds,” Wright said.

The structure of the buds themselves complicates the assessment. Each actually has three distinct buds: primary, secondary, and tertiary. The primary bud flowers and produces the main crop, but if damaged the smaller secondary bud will grow, but it will produce fewer flowers and a considerably smaller crop.

“At first, I thought only our Chardonnay was hurt because it was leafy, while the Pinot was still pretty tight in the bud,” winemaker Tony Soter said after surveying his Mineral Springs Ranch vineyard. “But it seems a little clearer that most of the Pinot primaries are damaged, but the secondary buds are showing more life. We worked on a frost event at the Beacon Hill vineyard in the early 2000s, and that demanded a lot of creativity, improvisation and ad-libbing.”

This is just the latest setback for Willamette Valley, which smelled smoky in 2020 from major wildfires in the area.

California Impact

To the south, California’s Central Valley and the Eastern Foothills experienced their worst frost in years, inflicting extensive damage and taking winemakers by surprise. “We were experiencing 90°F temperatures three days prior, so it was very strange weather,” said Stuart Spencer, executive director of the Lodi Winegrape Commission.

After a storm front passed in the early morning hours of April 12, the dew point dropped and temperatures dropped. Some areas suffered freezing temperatures for five hours. Spencer said he believes Clarksburg, southwest of Sacramento, suffered significant losses, but in Lodi the degree of damage varies by location. “The eastern hills were badly affected. Some vineyards lost almost 100%, with vines fried to the cord. Other areas were damaged in an intermediate way and others had no damage at all. been affected,” he said.

In Amador County, in the foothills of the Sierra Nevada, Bill Easton, owner and winemaker of Easton and Domaine de la Terre Rouge, reported similar results. “We had damage. I think around 25-30%, maybe less,” he explained, noting that the damage also varied by grape variety. The early grape varieties – Viognier, Barbera and Sauvignon Blanc – were the hardest hit. Easton’s winemaking practices may have helped. “We are pruning late to delay bud break. The first pruning shears were burned,” he said.

Nearby Terra d’Oro, winemaker Melissa Bordi said she suffered minimal damage to vineyards adjacent to the winery and tasting room. But other vineyards, including one behind the winery and others to the east of the winery, suffered greater damage, ranging from 40 to 60 percent buds. “Our hardest hit location is our Shenandoah Vineyard at the northern end of the Shenandoah Valley,” she said. “Planted in both Zinfandel and Barbera, we are seeing 60% losses.”

The UC Davis Department of Viticulture will offer a webinar on May 3 on identifying and mitigating frost damage in vineyards and will provide additional resources for affected winemakers.

Spencer expects Lodi’s yields to drop significantly which could be a blow. Lodi is a vital part of the California wine industry, with 110,000 acres of vineyards accounting for 20% of all wine produced in the state.

“We are so sad to have so much damage for the 2022 vintage,” Bordi said, “but we are optimistic that the remaining sprouts will be able to provide us with the expected quality of our wines.”

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