Grapevine bloom is about more than petals
The 2017 grape vintage is well under way. Ever since dormant vines awoke in March and bright green leaves started pushing out from the buds, winemakers have been watching each vine’s growth. The most critical time in a grapevine’s life is in May, when bloom occurs.
Did you know grapevines flower?
Those flowers eventually turn into fruit. “I think of flowering as the unsung hero stretch of the whole grape growing season,” says Plata Wine Partners winemaking director Alison Crowe, “We all say, yay, harvest, but that’s really the last hurrah.”
We met up with Crowe at the Stanley Ranch Vineyard in Napa Valley’s Carneros district to find out why she’s all about the bloom, and learned some cool things.
GRAPES SELF-POLLINATE >> Grapevines don’t need bees to pollinate, they do the job themselves. When a vine is about to bloom, tiny green BB-like buds start to swell. The green outer cap turns brown and pops off, revealing tiny white petals with pollen at the tip. Eventually the pollen falls back into the flower, resulting in the birth of a small, green grape berry.
BREEZES MATTER >> Vines need the right conditions to reproduce. “Your ideal weather is 80 degrees Farhenheit and very little wind,” Crowe says. “A light breeze keeps things dry and ventilated, but nothing violent.” That’s because the pollen can be easily knocked off the vine’s flower and dispersed. No pollen means no fruit set and no grapes.
HAIRY CLUSTERS ARE A GOOD THING >> Get up close and personal with a vine during bloom, and the clusters look like they’re covered in fine hair. “You want clusters to be nice and hairy,” Crowe says. “That’s a good indication that we will have a good fruit set.”
STORMS ARE BAD >> Wind, rain, cold temperatures and hail during bloom can wreak havoc. Winemakers watch weather patterns closely during bloom, although there’s not much they can do if a major storm comes through the vineyard.
SHATTER IS REALLY BAD >> Shatter — sparse or bare clusters — is what happens when vines don’t pollinate. Shatter was widespread in the 2011 and 2015 vintages, due to frost, wind and rain during bloom. The result: disappointingly small vintages. The longer bloom goes, the higher the risk of bad weather and shatter. The ideal bloom stage lasts 10 to 14 days. Crowe says the 2015 bloom took four weeks.
GRAPEVINE FLOWERS ARE FRAGRANT, TOO >> Crowe says during bloom, ephemeral aromas fill the vineyard. The Stanley Ranch Vineyard is planted to chardonnay and pinot noir. “To me chardonnay smells like melon and pear,” she says. “Pinot noir is more like apricot, peach and strawberry.” Crowe also detects a marine, saline quality in the fragrance.