Epic rains and a cold spring delayed SLO County’s grape harvest. How will it affect the wine?

The calendar has turned to November, and wineries around San Luis Obispo County are full of tired employees ready for this year’s delayed harvest season to be done.

“It’s been intense, gnarly and fast,” Janell Dusi of J Dusi Wines in Paso Robles said of a harvest that got off to a late start then suddenly kicked into overdrive when the fall’s first frost arrived last week.

This year, winemakers have been thrown a lot of hurdles (and blessings, they would add), from massive rainstorms in January and March, to the county’s coldest spring and summer in more than two decades.

“We’re not in charge, Mother Nature is,” said Neil Collins, the winemaker at Tablas Creek Vineyard and Lone Madrone in Paso Robles, a refrain that could apply across the state.

The heavy rains saturated drought-parched soils, letting nutrients that had long been sitting at the top of the soil column leach down to the vine roots.

“Without the rain, I think we would have been looking at a really bleak picture,” Collins said. “We really needed it.”

But the weather also slowed vineyards’ typical ripening schedules, pushing the harvest back and leaving wine fans to wonder how the 2023 vintage might be affected.

SLO County’s coldest spring and summer in more than 2 decades

This year’s heavy winter rains meant the soil stayed saturated for a long time. That moisture, though welcome, was then followed by colder than normal weather for the season.

This spring and summer were the coldest on average for San Luis Obispo County since 1999, according to climate data from the National Oceanic and Atmospheric Administration’s Centers for Environmental Information.

The chilly conditions mainly appeared to do two things: They allowed for mold and mildew to thrive, and they slowed down the wine grapes’ ripening process.

“We had a lot of issues with powdery mildew this year,” said Jean-Pierre Wolff of Wolff Vineyards in the Edna Valley. “It caused a lot of damage.”

Winemakers across the county faced a similar issue as Wolff: There simply wasn’t enough heat to kill the mold and mildew, meaning some varietals suffered.

“Since the soils were so saturated, that caused the ground temperatures to warm up slower than normal,” said Paul Hoover of Still Waters Vineyards in Paso Robles.

Cold temperatures delayed grape harvest

Winemakers usually wish for consistently warm temperatures so the grapes ripen evenly.

Too hot, and the grapes will ripen too rapidly and possibly ruin the balance of sugars and acids, which are part of what give the grapes their unique flavors.

This season’s consistently cold temperatures weren’t necessarily bad for winemakers, however.

“I think the cold makes the flavors better,” said Josh Beckett of Peachy Canyon Winery and Thibido Wines in Paso Robles.

But it did mean that wineries couldn’t start harvesting their grapes until about two to four weeks later than normal.

Typically, most wineries start harvesting their fruit around mid-August to early September, wrapping up before the end of October.

This year, many didn’t start until early to mid-September — and many hoped to finish harvests by the end of the week of Nov. 5.

That late start then introduced the potential for another wrinkle.

“It was going fine until last weekend (Oct. 28 and 29), when we got our first big frost,” Beckett said. “That hurt.”

The frost — an unusual occurrence during the harvest season because the process would normally be complete by now — threw winemakers into a frenzy.

“Once frost comes, your ripening season is done,” Beckett said. “Then it becomes: How fast can I get the grapes off the vines.”

Many California regions saw delayed grape harvests

Vintners in San Luis Obispo County certainly weren’t alone in their growing and harvest season adventures.

From the Napa and Sonoma valleys to the southern stretches of California’s wine-growing regions — nearly everyone appeared to have a later-than-normal harvest following the wet and chilly start to the year.

“Statewide, this has been a long, cool growing season,” said Federico Casassa, an associate professor of enology at Cal Poly in San Luis Obispo.

While the harvest season was uniformly late across the Central Coast, there was some variation in areas such as Napa Valley, Casassa noted.

In some of Napa’s areas, growers had wrapped up their harvest by the end of October, while others were still planning to pick well into the first and second week of November, according to reporting by the Napa Valley Register.

How will weather affect the quality of the vintage?

Despite the unusual growing and harvest season with the 2023 crop, winemakers aren’t fretting about the quality of wine they’ll ultimately produce.

“I’m an optimist with a good sense of humor, generally, ” Wolff said of his Edna Valley crop. “So I think it’s going to be a good year. But I usually tell people, ask me in three months after my wine is in the barrel and I’ve had a chance to taste it. But so far, so good.”

Hoover echoed that positive outlook.

“We’re getting a lot of really rich, natural flavors this year,” the Paso Robles winemaker said. “It’ll be a very unique vintage.”