Rain and windy weather causing problems for North Coast wine grape growers

May showers have put a damper across North Coast vineyards, wetting them at an inopportune time when they’re nearly blooming and raising the risk of damaged wine grapes and a smaller 2019 yield for certain varieties.

Because of the pelting rains and accompanying windy conditions, chardonnay and pinot noir grapes have the greatest chance to suffer from shatter, the term used by vintners when a grapevine’s delicate flowers don’t pollinate and develop into grapes.

The Carneros, Russian River Valley and Alexander Valley growing regions have seen those grape varieties already in bloom, vintners said. The full extent of the crop damage won’t be known for a few weeks until fruit set - when the small flowers are fertilized and transformed into tiny grapes. Then growers will conduct their grape cluster counts.

Following the unseasonably wet weather, local growers worry the predicted humid conditions could cause mold and mildew on the vines which would take an even greater toll on their grapes.

“It’s not ideal,” said Alison Crowe, director of winemaking at Plata Wine Partners in Napa, as she drove around the Carneros region near the San Pablo Bay. “It’s not necessarily impacted quality. It will impact the quantity.”

Another rain system was expected to pass through Sonoma County late Monday and dump another quarter-inch of precipitation, before yielding late Tuesday to dry and warmer weather, said Steve Anderson, a meteorologist with the National Weather Service in Monterey.

Santa Rosa has had 47.88 inches of rainfall since Oct. 1, the start date the weather service tracks in its annual rainfall total. That is more than 12½ inches above the annual average through Monday. Charles M. Schulz–Sonoma County Airport has registered 4¼ inches of rain so far during May as of noon Monday, almost 3 inches above average.

“The timing of the recent rain was not ideal, another curveball from Mother Nature. However, fortunately, we had only a small percentage of our vineyards going through bloom,” said Karissa Kruse, executive director for the Sonoma County Winegrowers trade group.

The Balletto Vineyards and Winery in Santa Rosa has 1% to 5% of its grape crop in bloom as of Monday, owner John Balletto said. However, he expects 50% of his crop to start flowering next week and he’s concerned about the high humidity in the forecast after the unusual heavy May rains.

“That could be a problem for pinot noir,” Balletto said.

Siduri winemaker Adam Lee estimated that 25% to 30% of the pinot noir crop in the Russian River Valley is in bloom and the winds that came with the recent rains also played a role in damaging flowers, including even breaking canes.

“It could be a little bit of loss of crop or a lot of loss of crop,” Lee said.

In Sonoma at Ram’s Gate Winery, about 50% of the chardonnay crop is in the flowering stage, said Joe Nielsen, director of winemaking. Nielsen said he doesn’t yet know the effect on the vineyard from the wet, windy weather because it’s been too muddy to drive tractors over it to assess.

“Right now, it’s just sort of wait and see,” he said.

Even those who haven’t had any of this year’s grape crop bloom on their vineyards are concerned with the weather. This year’s growing season is coming off a 2018 harvest that reached a record $2 billion in value with mostly high yields across Sonoma, Napa, Mendocino and Lake counties.

Domenic Carinalli, who has about 100 acres of pinot noir, pinot gris and chardonnay just east of Sebastopol, said his vines are probably about a week to 10 days from flowering. His crews are on guard for other problems the rain could create beyond disrupting the flowering grapes in their infancy.

A major concern of his is possible mold and powdery mildew on the vines as humidity builds up in the canopies on the vineyards. Crews will have to resort to removing more leaves along the vines to let the air inside to dry them, as well as deploy targeted spraying with sulfur, Carinalli said.

“That’s a concern with everybody,” Carinalli said of the potential mildew.

In addition, growers will have to check if the rains have triggered suckers, which are excessive shoots growing from old wood that don’t contain any fruit, but drain energy from the vine. That will require more work to remove them, as well as trimming overgrown cover crops between the vines.

“Vineyard managers need to be on high alert for this whole period between flowering and fruit set,” said Ken Wornick, a Sonoma-based consultant who also has a vineyard. “It’s going to be hour by hour. ... Some are going to get lucky and some are going to get stung.”

Growers have been trying to stay positive despite the heavy spring rains because they realize they can’t control weather.

“You are playing the card that Mother Nature has dealt,” said Cameron Mauritson, vineyard manager at Mauritson Farms in Healdsburg, which has only been affected with some bloom on chardonnay vines in the Alexander Valley. On the bright side, he said the precipitation will result in less irrigation on vines in the coming months. “We’ll have great soil moisture going into summer,” Mauritson said.

You can reach Staff Writer Bill Swindell at 707-521-5223 or bill.swindell@pressdemocrat.com. On Twitter @BillSwindell.