Usually not. However, in some years vines may be overcropped if too many buds were retained at pruning or if the buds prove to be more fruitful than anticipated. Too many clusters will tax the vine’s capacity to ripen them because there will not be enough leaf area for sufficient sugar production. Short shoots are one sign that a vine’s capacity is over-taxed. If a grower has difficulty ripening a crop to the level required by the winemaker, thinning can help. However, thinning must be practiced early enough to have an effect, i.e., thinning a week or two before harvest will not leave enough time to see the desired effect. Thinning is often done at veraison or before. The need for thinning is also determined by comparing a phenological stage, such as flowering or veraison, to normal calendar dates. When the year is “late” there may be insufficient growing season remaining to ripen the crop, necessitating some thinning.

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