Between the Vines is a biweekly column on wine and wine making in the Livermore Valley region. This information was contributed by Michael Princevalle, of Coastal Viticultural Consultants. A member of the Livermore Valley Winegrowers Association, CVC manages several local vineyards, including vines at Ravenswood Historical Site in Livermore.
What's happening in Livermore Valley's vineyards this month?
At this time in the Livermore Valley, things seem to be quiet in the vineyards. Since nature has given us a dry winter, most, if not all, the vineyards in the valley are pruned, and mowing of weeds and cover crop and mulching of prunings have begun. Now, with the advent of warm temperatures and longer days, the vines in the valley are beginning to experience "bud-break;" shoots will emerge soon after. So, ready or not, the 2013 growing season is springing forward.
Once bud break occurs, vineyard managers will commence their vigil. This time of year, and through the next month, the buds and young shoots of the vines are very vulnerable to pests and weather. For example, cut worms can emerge from the soil, crawl up to the buds and damage them. Voles and other critters also can attack the buds and emerging shoots and cause enough damage to affect yield. Regardless of the nature of the pest, damage to buds or young shoots can have a significant impact on a year's yield. Though the occurrence and damage by these pests are commonly not significant, if they occur in your vineyard, it's significant. A local pest control adviser can most likely offer remedies for these pests if they occur.
Weather conditions are also worrisome to vineyard managers. Frost can have a devastating impact on buds and young shoots, and therefore, a significant impact on a year's yield. Frost damage is not a typical or widespread problem in Livermore Valley, but it can strike certain areas of the valley and specific areas within a vineyard.
Most vineyards in our valley do not have the wind machines or overhead sprinklers that are used in other grape growing regions to prevent frost damage. To mitigate the potential for frost damage, grape growers in Livermore Valley work hard to ensure that ground cover or weeds in the vineyards are sufficiently mowed (or tilled) to allow maximum sunlight to reach the soil. This allows the soil to warm during the day and radiate heat into the vineyard at night. Nighttime radiant heat from the soil can make a difference of a degree or two in the vineyard, which can be just enough to avert frost damage of tender buds and shoots. Also, since cold air tends to flow like a stream and low to the ground, keeping weeds or cover crop mowed short allows the cold air to more readily flow out of the vineyard and not stack up against tall weeds, where it can reach tender portions of the vines.
So, though it seems serene in the vineyard this time of year, there are plenty of things ready to spring out and attack a vineyard!
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