caring for dormant vines
While the vines are sleeping in the winter, it's time to prune. Grapevine pruning focuses the growth of the vine where you want it, and determines how much fruit a vine will have. Each vineyard is different, with the variety of grape, location, fertility of the soil and climate all playing a role in the decision on how to best prune.
For pinot noir, Dutton Ranch aims for 2.5 to 4 tons per acre, depending on the vineyard. Many of Dutton-Goldfield's pinot vineyards produce far less—frequently lower than 2 tons per acre. For a target of 4 tons, the math is 2 bunches per bud and 20 buds per vine for a total of 40 bunches. It takes about 5 bunches to equal a pound, so that gives you 8 pounds per vine. Multiply that by 1,089 vines per acre and you come up with 4 tons per acre.
This assumes all goes according to plan, and each bud does its job of producing 2 bunches, and each of those bunches is full of beautiful, plump, juicy grapes. Of course, this almost never happens, as weather during bloom in May and June affects the set and the ultimate harvest. Not only does it have a direct impact on that year's harvest, it also dictates the following year's crop, since the buds are actually deciding how many bunches and shoots they'll put out the following year at this time as well.
The main types of pruning done in our vineyards are cane, cordon and head pruning. Cane pruning is used in the cooler areas, as it helps to set a better crop in these sites. At pruning time, up to 4 new canes from the previous year are trained onto the wires out to each side of the trunk (2 per side, ideally), to a point midway to the next vine. Each of these canes will have 8 to 10 buds. This is a much more time-consuming pruning process, as you need to make a decision vine by vine on the best canes to keep to create the right shape and fruitfulness.
With cordon pruning, the old wood remains trained on the wires, and the spurs on the arms of the vine are the fruiting wood. The previous year's spur will have produced 2 canes: typically, the lowest of these 2 canes will be used, and pruned down to the lowest 2 buds on it; the higher cane will be cut down below its lowest bud. In this way, a new spur (with 2 buds and 2 bunches per bud) is created each year. Head pruning is basically the same as cordon, but rather than being trained on wires out to the side of the trunk, the canes grow straight up in a more casual form.
Whatever method is used, with all pruning, it's all about balance: deciding just the right amount of fruit each vine and vineyard can comfortably ripen to perfection.