Grape growers are watching the weather reports with dread.
The late-season downpour hitting Northern California is threatening to devastate this year's grape crop, making it potentially the third weather event in the last four years to wreak havoc on vineyards.
“It's causing us a lot of frustration,” said Steve Hill, general manager of Durell Vineyard in Sonoma.
Most vineyards across Sonoma County are now in some stage of bloom, a process where plants engage in the delicate dance of self-pollination in order to fertilize the eggs that will become grapes.
Rainfall in June, which forecasters predict could set a new record, is expected to lower the amount of grapes that vineyards produce, potentially costing Sonoma County growers tens of millions of dollars in lost revenue at a time the industry continues to suffer economically.
“In reality, we are taking a loss every time these storms come in,” said Steve Thomas, director of vineyard operations at Kunde Winery. “This crop is definitely getting smaller.”
Grapevine fertilization is timed to normally occur after the rainy season. But the late rain this year is hampering the process, preventing some grapes from forming.
For instance, small caps located on the tip of a grapevine's many flowers usually pop off sometime in late May or early June. But this year's heavy rains can make the cap stick to the flower, hindering fertilization.
The wet weather also can bog down pollen spores, preventing them from alighting on the flower's eggs.
“This doesn't mean that grape growers are going to have a total bust, but we might not have as much as we'd hoped,” Hill said.
The impact of the potentially record-setting rain will not be known for a few weeks, when growers will be able to identify and count how many flower clusters successfully fertilized and bear the earliest signs of grapes — called fruit sets.