Flower Power

The appearance of tiny green flowers on the grape vine is perhaps the most critical juncture in the vineyard’s annual cycle. It occurs six to thirteen weeks after budburst, the moment in early spring when buds swell on the vine and erupt into a crown of foliage. You could easily miss it. Flowers on a grape vine are the color of their host plant and the size of a button on a dress shirt. Winemakers watch them like hawks because within a few weeks each flower will shed its petals, self-pollinate and transform into a nascent grape. Since each flower that fertilizes becomes a nascent grape, floweringdetermines both the size of the vintage and whether or not all the fruit in the vineyard will be at the same state of evolution come the harvest. For most winemakers, it is a real nail biter. 

In most of the northern hemisphere, a good flowering occurs over the course of three or foursun-drenched days in early June. If the weather is too wet or too cold, the flowering will be uneven. Worse yet, horror stories abound of entire crops being lost to hail, freezing rain, wind, or even too many clouds. 

Ideally, flowering is followed by two weeks of temperate weather during which the blossoms transform into berries. Many vintners leave their vineyards alone throughout this period for fear of disturbing the natural process. Even under the best circumstances, flowering does not happen entirely at once. It is staggered by grape variety and a vineyard’s exposure to the sun. In California, chardonnay blossoms first, followed by pinot noir and merlot, then cabernet sauvignon and petite verdot. 

Chris Howell, the winemaker at Cain Vineyard & Winery on Spring Mountain, describes flowering in the Napa Valley as a tight wave that moves up from Carneros, to Napa to Yountville and beyond. He calls it, “a reproductive moment and strong marking point,” since prospective harvest dates are calculated as one hundred to one hundred ten days after the event.