Rain, rain and more rain. How do Sonoma County vineyards cope?

January’s powerful storms have brought a startling sight to those traveling through Sonoma County: entire vineyards swallowed by water — a result of this winter’s immense rainfall and subsequent flooding.

For some, the sight of their favorite Russian River pinot noir vineyard under 6 inches of water might produce a sense of unease.

Can a vineyard survive under water?

“During this time in the season, the grapevines are dormant, so the recent storms, rainfall and flooding has not damaged the vineyards or impacted overall vine health,” said Karissa Kruse, president of Sonoma County Winegrowers. “Our local grape growers have primarily been focused on cleaning up debris, fallen trees and dealing with flooded roads.”

From late fall to early spring, grapevines are in a deep slumber, like a gardener’s favorite perennial. During this time, their root systems don’t need access to oxygen or nutrients, so they’re often impervious to standing water above.

The main concerns with vineyard flooding can come in the form of soil erosion, eutypa dieback (a fungal disease that can affect grapevines) from pruning in wet weather and “wet feet” — an ailment akin to root rot in a houseplant.

Cornerstone Certified Vineyard, Sonoma County

For Jim Pratt, a veteran grape grower and owner of Cornerstone Certified Vineyard in Sonoma County, the significant rainfall has been manageable so far (“knock on wood,” he said). Yet soil erosion is his biggest concern.

Pratt and his company manage 16 vineyards and a total of 350 vineyard acres in Sonoma County which supply fruit for wineries like Kosta Browne, Gary Farrell and Twomey.

“Even in drought years, we prepare for rain by putting erosion controls in, like hay bales and straw waddles, which don’t stop the flow of water but slow it down,” Pratt said. “Right now, we have crews clearing brush and branches so we can make sure the water is diverted into reservoirs.”

Well water is his vineyards’ primary water source, so he’s hopeful the rain is recharging the local aquifers.

“After three to four years of drought, it’s great to finally have the chance to do that,” he said.

For now, Pratt is crossing his fingers the heavy rains don’t last until February, which would cut into pruning time. Typically, winter pruning already has begun, yet the rains have made it too difficult to get into the vineyard so far this year.

“We like to be done with pruning by the middle of March, so that’s probably the most frustrating part about the rain,” Pratt said. “We’re not panicking yet, but we’re thinking about it.”

Emeritus Vineyards, Sebastopol

At Emeritus Vineyards in Sebastopol, where 5 inches of rain fell in 72 hours, Assistant Vineyard Manager Riggs Lokka is concerned about excess water flow and soil erosion, too.

In October, his team planted cover crops throughout the vineyard. Those crops can help mitigate erosion, but he said the cold weather has slowed their growth.

The dry-farmed vineyard has been fortunate to escape major flooding, as much of the excess water runs off the ranch and down to Atascadero Creek.

“The rain has been a great thing. I just wish it wouldn’t come down half an inch per hour,” Lokka said. “The past couple years have been so dry, so these moisture levels are really going to benefit the grapes and their vigor once they bud out.”

Rodney Strong Vineyards, in Alexander Valley

In Alexander Valley, Rodney Strong winery’s sauvignon blanc vineyard has been experiencing intermittent flooding, but Estate Vineyard Manager Alli Dericco said grapevines are resilient.

“As long as they are asleep, they’re fine. It’s when we have late- season flooding when the vines are awake that we have a problem,” Dericco said. “Also, vines that have been submerged in water too long can suffer from wet feet.”

Waterlogged soils can deprive a grapevine’s roots of oxygen. Over an extended period of time, this can limit the vine’s uptake of water and nutrients — a condition called wet feet.

Soil composition and its drainage capacity can determine whether a vine is more or less susceptible to wet feet.

Goldridge soil, the fine-grain sandy loam found throughout much of Sonoma County, is known for its exceptional drainage abilities, so wet feet in these areas isn’t as much of a concern. Clay soils, which can collect and pool water, are a bigger concern.

“The amount of rain we are getting is so nice, and it’s great to see our local lakes and reservoirs filling up,” Derrico said. “If we get sporadic rain into the spring, I think it will give everyone across the board a chance of a great growing season.”

More rain ahead

Weather forecasts predict the parade of atmospheric rivers hitting Sonoma County won’t end any time soon. In the meantime, Karissa Kruse is thrilled with the rainfall.

“Many grape growers throughout the county have invested in reservoirs and ponds to capture and store rainwater for future use,” Kruse said. “These recent storms have quickly filled these reservoirs and ponds, which should more than satisfy the irrigation and frost protection needs later in the harvest season. Overall, the current rains have been extremely beneficial.”

You can reach Staff Writer Sarah Doyle at 707-521-5478 or sarah.doyle@pressdemocrat.com.