In wine country, the gentle cadence of the seasons grows stronger with each stage; it begins softly in winter when the vines are clipped and bare, and steadily intensifies through the first signs of life at bud break, becomes steady but more urgent during the slow pace of summer, when gloriously green vineyards sway across the valley, marching in time toward the crescendo of harvest.
Small, green berries began forming in late spring during fruit set, and now the berries begin to form clusters that will eventually become bunches of grapes. When vines are left to their own devices without trellising or trimming, they have a savage beauty, growing high and wild like the fictional vines of Jack and the Beanstalk. You won’t see wild vines much in Napa Valley. Instead, today’s viticulturists use science and data to calibrate grape production. With few exceptions, vines are practically identical in each vineyard, adding a sense of symmetry that brings peace to the valley.
But there is work being done, although most of it is imperceptible—the fruit is slowly maturing.
Mother Nature poses one of the biggest risks to the fruit during this time. Too little rain can be remedied with irrigation, but too much rain can be catastrophic. Too much sun can damage the grapes or cause them to ripen too soon. Too little sun and the fruit may not reach its full flavor potential or may be too acidic or tannic.
Human hands come into play with the use of vine management techniques. To counter less-than-ideal weather, vineyard specialists use grapevine leaves to regulate heat. If more sun is needed, more leaves are removed to give them every opportunity to soak up the rays. If less sun is desired, the leaves will remain, shading the grapes as much as possible from the heat. Vine and fruit growth can be limited to improve fruit quality, or encouraged, to increase quantity.
The extended sun exposure in summer pushes fruit to maturity, while the cool nights help maintain acidity needed for flavor balance. And then, in late July and August, something magical happens in the Napa Valley vineyards—the fruit changes color and begins ripening. This is known as veraison. What started the season as small, green, hard spheres become plump, colorful grapes, red and purple for red varieties and golden or translucent for white varieties. The grape growth slows during this period, the vines begin focusing all their energy into causing sugars in the fruit to increase and acids in the fruit to decrease, showing the first real indicator of the quality that can be expected from the year’s crop.
Veraison is a turning point in the vineyard and begins the final drumbeat to the big finale of the year. The timeframe differs by grape variety and growing region, but in general, 30 to 70 days from this color change, Napa Valley fruit will reach its peak and be ready to harvest.
Layne Randolph, Inside Napa Valley Magazine, August 2019