Cluster Formation: A Timeline
As the unofficial beginning of summer nears with Memorial Day just around the corner, the vineyards here in Napa are beginning to take shape. Here is a photographic journal of grapevine development so far.
March 5th, 2014. Bud break. Moderate rains return to the valley after an unusually mild and dry winter. Daytime temperatures are in the sixties, and nighttime temperatures are now steadily in the forties. With a steady accumulation of warmer days and nights, enzymes within these Chardonnay vines trigger bud break in the Oak Knoll area.
March 18th, 2014. Shoot development. Warm weather continues, and a few short-lived rain storms bring much-needed water to that valley. Red varieties, like this Syrah vine in St. Helena, are rapidly developing leaves and cluster flower buds. These tender young shoots are particularly prone to frost damage at this time of year.
April 16th, 2014. With a bit more moisture in the soil combined with warm days, the shoots are growing very quickly with fully developed leaves. The cluster flower buds are fully formed now and are very close to bloom.
May 6th, 2014. White varieties, like this Chardonnay vine, are have been in full bloom for about one week. Grapevines are self-pollenating and will rely on a steady breeze and moderate weather to realize full germination. Radical swings in temperature, heavy winds or rain can impede the flower’s ability to germinate healthy fruit. A poor “set” of berries in the cluster is called “shatter”.
May 18th, 2014. The same Chardonnay vine is now fully “set”, as we say. From this point onward, we can begin to make our harvest yield predictions based on the average number of berries per grape cluster multiplied by the average mature berry weight.