John Clendenen lifted his muddy leather boot and gave a swift kick to a cabernet grapevine tucked away in the rolling ridges between Windsor and Chalk Hill. A light shower fell from the vine onto the already water-logged soil.
?Here?s problem A,? said the veteran Healdsburg vineyard manager, pointing to a cluster of dark purple grapes marred by bunch rot. ?The cabernet ... it?s just anyone?s call at this point. I was surprised to see so much rot.?
The heavy rains that drenched the North Coast this week didn?t last long. Few, however, expected a week of unrelenting moisture, fog and overcast skies that, when coupled with Thursday?s temperatures in the high 60s and low 70s, created textbook conditions for what is technically known as botrytis rot.
?Seventy degrees and moist ? it doesn?t get any better for mold,? said Ron Vann, who owns the vineyard Clendenen was reviewing Thursday afternoon.
Clendenen said ripe grapes don?t know when to stop taking water. They?ll continue to absorb moisture, diluting sugar levels and increasing the possibility that softer-skin varieties, such as chardonnay and zinfandel, literally split open.
?Here?s a grape that wants to split,? he said, pointing to a dark line that ran across the surface of the grape, resembling the ?linea nigra? pregnant women get below their belly button.
?Actually the rotten berries don?t taste bad,? he said after trying a grape not yet covered by the grayish mold.
Clendenen said he would be out Friday ?leafing? Vann?s crop, yanking vine leaves away from the bunches to increase ?air movement? and allow grapes to dry out and prevent further rot. For vineyard owners, that process is a cost they would not have incurred had it not rained.
?You try not to let it bother you but you hate to see good grapes go to waste,? said Vann. ?But one thing you can?t control is the weather.?
The dreary, humid weather that hung over the North Coast on Thursday was a unique phenomenon in the state, said Steve Anderson, a forecaster for the National Weather Service.