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Grounded Grapegrowing GLENN MCGOURT Y Making Sense of Canopy Management C anopy management is an es- sential part of growing high- quality winegrapes. Many of the practices are expensive, require careful timing and also may prevent disease, improve fruit color and ultimately make better wine. This past spring I attended two industry seminars about canopy management with very new and updated information. Timing is very important for most cano- py-management practices, as you are try- ing to take advantage of the vine's growth stages and built-in controls for growth and fruit ripening. Winegrape vines are unusu- al from a horticultural perspective because annual pruning is so severe. Most of the previous season's growth is removed in the winter. During an eight-week period that starts at bud break, the vine rebuilds its entire canopy (stems and leaves) while also blooming and setting a crop. Then the vine changes purposes and begins to mature seeds and ripen fruit as a survival strategy: Make good-tasting ripe fruit that will en- courage various creatures to eat and dis- perse the seeds. That is the vine's mission, but our mission is to make great wine, so we manage the vine for an outcome of making high-quality fruit. Our approach to canopy management has profoundly changed in the past 30 years. Pio- neers including Norm Shaulis, Mark Kliew- er, Cesare Intrieri, Richard Smart and Alain Carbonneau (and all of their many graduate students and post docs) have revolutionized canopy management practices that have re- sulted in much-improved fruit quality. We are now in a period in which labor has become less available and more expen- sive, and winegrowers constantly have to assure themselves that the canopy-man- 72 WINES & VINES SEPTEMBER 2012 agement practices they are undertaking are worth the expense and are actually helping to make better fruit. Are the practices pro- moting or delaying ripening? Is fruit-ripen- ing uniformity improved or not affected? Fruit-to-pruning ratios greater than 10 may be slow to ripen and often do not have very good concentration of flavor and color. Fruit thinning It is commonly accepted that quality wine comes from balanced vines, or vines with a ratio of 5-10 pounds of fruit to 1 pound of prunings (fresh weight.) This is actually a shorthand way of saying that you need to have 10-14 cm2 of leaf area per 1 gram of fruit. Some winemakers like fruit that comes from 3 pounds of fruit per l pound of prunings, as the resulting wines are of- ten quite concentrated and full bodied. Problems occur when the large canopies on these vines promote early sugar ma- turity without tannin maturity (especially with Cabernet Sauvignon.) The fruit takes more time to fully mature, and the result- ing wine may have very high alcohol, as sugar continues to accumulate. The oppo- site problem happens when too much fruit is left on the vine: Fruit-to-pruning ratios greater than 10 may be slow to ripen and often do not have very good concentra- tion of flavor and color. A fruit-to-pruning ratio of 5:1 still results in very good wine with ample alcohol, good concentration and good color in most cases. How will you know when you have too much fruit on your vines? Many people will thin to two clusters per 36- to 42- inch shoot. If clusters are quite large, one per shoot may be adequate. Research has shown that thinning is best done early in the season rather than later if the purpose of the crop-load removal is being done to advance fruit maturity. If you sense that a short season is likely, you are going to be better off removing fruit soon after fruit set to speed up ripening. The longer you wait, the less difference it will make in accelerating ripening. You can expect up to 10 days advancement in ripening if thinning is done after berry set, removing 20%-40% of the clusters. The same fruit thinning at veraison (fruit coloring and softening) may only accelerate ripening by four days. If you wait three weeks later to thin, it probably won't accelerate ripening at all. So thinning fruit early is good if you are expecting a short or late growing sea- son, and you feel that it is going to be dif- ficult to ripen the crop. Anthocyanin concentration in fruit also shows more of an increase when thinning Highlights • This article summarizes the latest research about winegrape canopy- management practices. • Timing is absolutely critical to achieve the desired results (e.g., fruit thinning early in the season will advance harvest.) • Excessive leaf pulling on VSP trellis sys- tems might result in unbalanced wines with reduced color. • Balancing the fruit to the canopy's leaf area is still an important object of fruit thinning.