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GRAPE GRO WING sunburn and dehydration. Additionally, sunlight on the shoots will improve bud fruitfulness the following year. Most Napa Valley winegrowers retain about five shoots per foot of canopy. The spacing of the shoots generally allows for optimum sunlight on the leaves. The shoot length on a balanced vine should be uniform and grow to between 3.5 feet and 5 feet by veraison (the point at which the grape berries turn from green to their final color, representing the change from berry growth to berry ripening.) The shoots should stop growing about two weeks before veraison and retain about 12 to 15 active leaves that remain green and healthy until harvest. The grape clusters typically are protected by filtered light through one or two layers of leaves. Growers may decide to remove basal laterals or laterals plus a few leaves based on observations of the site and leaf cover. Row direction and leaf size (Merlot and Zinfandel are variet- ies that have large leaves) will influence the decision about leaf removal to obtain the desired amount of fruit exposure. North-by-south row direction may require leaf removal on the east (morning sun) side and no leaves on the west side of the canopy to shade the fruit. This drip-irrigated vineyard uses a Geneva double curtain trellis spaced 12 feet by 6 feet. ValleyPipe_Nov06 10/6/06 6:30 PM Page 1 The water status of the vine has a major effect on the canopy and ultimate fruit and wine quality. As such, irrigation management is one of the most important viticultural tools. The Napa Valley gener- ally receives enough rainfall from Novem- ber through April to fill the soil profile. Normally, very little rain occurs during the summer and fall months. Almost all Napa vineyards are either dry farmed or Wines & Vines nOVeMBeR 2011 35