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08/01/2011

Veraison: The Turning Point

One of the most important turning points in California’s annual wine grape growing cycle is known as veraison, or the onset of ripening. This is the time of year when wine grapes begin to soften and turn color, readying themselves for the accumulation of sugar and the final sprint to harvest. Depending on the growing region, the grape variety and the particular characteristics of the growing season, veraison usually occurs sometime between early- or mid-July to early-August, signaling to the grower that there are only a few weeks left until picking.

“We usually have about six to eight weeks from the start of veraison to full berry maturity,” notes Diego Olagaray of Olagaray Brothers, which farms 1,000 acres of wine grapes (as well as alfalfa, corn and tomatoes) in the Lodi, California region. “It’s an excellent gauge of when we can expect harvest to begin.”

While much of the grapevine’s activity up until veraison has been focused on shoot and leaf growth and setting the crop, when veraison gets underway the action is in the berries themselves. With red varieties such as Zinfandel, Pinot Noir or Cabernet Sauvignon, it’s easy to tell when veraison is happening, since the grapes begin to turn pink then red. With white varieties it’s not quite so obvious; some, like Chardonnay and Sauvignon Blanc, turn from green to golden yellow. Pinot Grigio, on the other hand, turns a brownish root beer color.

While each variety has its own particular shade, there’s more to veraison than turning color. “The grapes can nearly double in size during this period; the skins get thinner, the content gets fleshier, and we start to see veining in the fleshy tissue,” says Olagaray, who notes that with some of the white grapes, they need to actually feel the grapes to see if veraison has begun. “This is also when we see sugar accumulation and seed development.”

As one might expect, California’s wine grape growers are especially busy in the weeks leading up to and during veraison. Managing the grapevines’ canopies – pulling leaves and tucking shoots up into the trellis systems – is a big focus as growers carefully control the amount of air and sunlight that surround the grape clusters, encouraging grape development and lessening the potential of damage from mildew. Depending on the vineyard, some growers thin their crop prior to veraison, pulling excess fruit so that the vines can concentrate their energy on ripening the clusters that remain. And from the time fruit set has occurred up to and through veraison, growers are also intensely focused on irrigation, making sure that the vines have enough water to maintain healthy canopies, but not so much that the flavor of the fruit is diluted.

“Drip irrigation allows us to finely tune the amount of water we give the vines, which is critical during the hot summer months,” says Olagaray. “Each cluster on the vine is like a sink, sucking up water and nutrients. As the vines go from a vegetative to a fruitful state during veraison, we can spoon feed the amount of water we give them, accelerating or decelerating as the season and climatic conditions dictate.”

Keeping an eye on the nutrients the vines are getting is another way of maintaining a healthy vineyard in the long term, and Olagaray and other growers use “petiole analysis” – where the stems of the grape leaves are dissected and analyzed – to determine if the vines have the proper amount of nitrogen, potassium and phosphate. Depending on the result, a grower may decide to “fertigate” (apply fertilizer via the irrigation system), to supply the vine with the nutrient it requires. This analysis, which is typically done at bloom, during veraison and just prior to harvest, may also determine what adjustments the grower needs to make for the following growing season in terms of cover crops or soil amendments.

“Although harvest is never far from our minds once veraison has begun, we still have our eyes on the future,” says Olagaray. “The next growing season is just around the corner.”

Veraison is when wine grapes begin to soften and turn color in preparation for the accumulation of sugar.