Every year, starting in late February to early March, we prune all of our 38,000± grapevines. We select the time based on when the weather is reasonable and the vineyard floor is not too soft, but it is always near the end of winter.
We prune in two steps: long pruning first, and then, beginning in mid-April, short pruning. In long pruning mature vines, we cut off most of last year’s growth, leaving canes that are 6–8 inches long with 5–6 buds on each cane. Most of this work is done with our V-Mech mechanical pruning system. While pruning is very fast with the V-Mech, we do have to return and pull out very long canes manually. In select varieties we also remove any dead wood or do selective pruning to replace any damaged or under producing cordons.
On vines less than 3 years old, we do the work manually and focus on shaping the vine so it has a strong trunk and a sturdy cordon along the top wire. We focus on the structure of the vine to accommodate the V-Mech pruner for pruning in the future and larger crop loads.
In April, we return and manually remove all but 2–3 buds per cane. This work goes very quickly.
Actually, it is a bit more complicated than that because we determine first how robust the vine is in order to give us an estimate of how much fruit the vine will produce without injury to the vine itself. This measurement is taken right at the beginning of pruning in February by completely pruning one vine of each variety and weighing the amount of pruned wood we remove. The heavier the pruned wood, the greater the fruit load can be. We leave more buds on the vine if we think it will produce more grapes without damage to the vine itself.
The objective of pruning is to optimize the volume of fruit we can potentially harvest, to maximize its quality, and to simplify the mechanics of harvest. We control the volume of fruit by controlling the number of buds we leave. We influence the quality of the fruit by shaping the vine so that the fruit can get sunlight as it matures. And, we simplify harvest by keeping the fruit in a “harvest zone” on the vine.
Pruning actually takes more time than harvesting does, but it is spread out over two months whereas harvest has to be done right when the grapes are at their peak.