After harvest, when the wines are aging in barrels, the vines begin losing their leaves and become dormant. Pruning, the major winter vineyard work, can be done any time between leaf loss and bud break. However, we usually start the process in January when the canes have become very woody. Fruit is produced only on shoots from one year old canes; therefore strong new canes must be produced every year to maintain good production. Pruning is used to remove extraneous canes and to retain a small number of good ones. Canes are selected for two purposes: to provide shoots for the coming season and healthy shoots for the next dormant season.
Figure 1 illustrates a grapevine structure before (right side) and after (left side) pruning. The new fruiting cane on the left has been selected and tied to the wire; its buds will provide the shoots on the right during the growing season. Watersprouts and suckers (from the rootstock below the graft) are removed during the growing season.
Figure 2 shows the pruning that resulted in the trained vine on the left of Figure 1. Note the renewal spur retained for next season’s fruiting cane.
The bud count is the number of dormant buds retained on the fruiting cane at pruning. Too many buds can result in a crowded canopy with excessive shading and a high crop load that the vine may not be capable of ripening. Therefore pruning is perhaps the most critical tool for managing a vineyard to obtain the best possible fruit from the site.
The weight of extraneous vines removed at pruning – pruning weight – is used to estimate the bud count. Formulas, based on pruning weight, are useful in estimating bud count. One is to retain 20 buds for the first pound and 10 for each pound thereafter of pruning weight. The aim is to retain more buds that will increase the crop load and balance the vine better. Later in the season buds are removed as needed to adjust the crop load.
Now to the real vineyard. In our Pinot Noir vineyard we are using single cane pruning as opposed to two canes as shown in Figure 1 above. When vine spacing is above approximately 4 feet or more it is usually necessary to use two canes to fill the canopy. Our vine spacing is 4 feet but the vineyard is vigorous – therefore single canes.
Photo 1 is the vineyard before pruning got underway. Photo 2 is after the extraneous vines were cut and removed. The fruiting cane and a spare cane are shown. In Photo 3 the fruiting cane has been tied to the wire