Anther fully extended

The Sex Life of Grapes

Flowers are everywhere in the spring in Northern California. On the sides of roads, in the cracks of sidewalks, between the rows of vines, clutched between your teeth. Roses are in full blush, patches of wild poppies dutifully perform their open-close routines with the rising and setting of the sun and the slutty manzanita bushes expose their sticky stamen to hordes of hummingbirds. The vines too are flowering, although it is a less dramatic affair “compared with many other plants,” writes Jancis Robinson, MW. “The vine has unattractive small green flowers and the flowering process in the vineyard is so notably unspectacular that it is likely to be missed by the casual observer.”

Up until now, the clusters we’ve seen have been exactly those small green flowers. This week, they started to open up. The flowering process can take weeks — or days — depending on the weather. The sequence of events goes something like this: the individual flowers open, the cap, or calyptra, which fuses the petals together, is shed, releasing the pollen which then fertilizes the ovary, forming seeds and ultimately grape berries. “Most wine grapes have perfect, or hermaphroditic, flowers — that is, with well-developed and functional male and female parts,” says Robinson.

Flowering, as you can imagine, is an important time in the vineyard. If it’s too hot, too cold, too wet, too windy, those flowers will simply not set and will instead blow off and fall to the ground, a process known as shatter.

“The key for all farming is moderation,” says Tegan Passalacqua, winemaker for Turley Cellars. And flowering time is no different: “You don’t want the highs and the lows.” This week in his zinfandel vineyard in Contra Costa, Passalacqua saw what he describes as “the fastest I’ve ever seen anything flower, ever.” Six days. The same vineyard last year took nearly three weeks thanks to rainy and windy weather. “When things flower quickly you get great fruit set and cluster weight,” says Passalacqua. (Even under perfect conditions only about 30 percent of flowers will become berries.)

Turley’s St. Helena vineyard has just started flowering and in Amador County, where soil temperatures are moderated by snow melt and the vines are notoriously behind, has yet to begin. Passalacqua, and grape farmers everywhere, are hoping for calm air, moderate temperatures (the mid-80s will do) and of course, no rain. We are happy to report that his week’s forecast (for Napa Valley, at least) is exactly that.