It’s been an unusually cool spring throughout California grape growing areas and the crop is developing significantly slower than normal. Even in late May, Sonoma County grape growers were turning on wind machines for frost.

“Most growers here agree it’s about three weeks later than last year,” says veteran grower Duff Bevill, Bevill Vineyard Management, Healdsburg, Calif.

He describes the slower pace in one block of Chardonnay, located in a warmer part of the Alexander Valley near Geyserville. It’s usually the first to bloom, typically around the first of May. This year it didn’t begin blooming until mid-May. As of June 10, he says, bloom had not begun in quite a few of his blocks.

For those that have bloomed, the late start has been followed by a longer-than-normal blooming period, which has produced a wide variation in development of berries within bunches.

“There’s as much as three weeks difference in maturity among the berries on the same cluster,” he says. He expects that this year’s harvest will not only be delayed, but managing it will be more challenging because of the mixed maturities of the grapes.

“We’re likely to have unripe and overripe berries on the same cluster,” Bevill says. “It will be tougher to make the right call for when to harvest the grapes. It will be easy enough to measure Brix, but deciding when the fruit is ready will be much more difficult. Things should be quite interesting as winemakers decide when to harvest a particular block. It will be harder for rookie winemakers than those with experience.”

He recalls a few years back when there was a big difference in the maturity of individual Zinfandel grapes at harvest.

“An unusually large number of tiny shot berries remained on the clusters until the day we picked,” Bevill says. “We picked when we thought the mature grapes were ripe. The fear was that we’d have all the green berries in the fermentation tank and they would break down and give off an unripened flavor. It will be quite interesting to see how this season develops.”