Every winter canes on vines are pruned back to their "spurs" , i.e. a thumb sized stump every 6 inches along the cordon. The cordon is the branch of the vine that grows horizontally from the trunk.
Every 6 inches is a spur, and from that spur the canes emerge each spring. Canes from the prior year are cut back to a few inches long, with 2 potential buds on each spur.
So when is the best time to prune ?
TWO THEORIES TO CONSIDER
Late Pruning
This will retard the growth of new buds during frost season, thru reducing the chances of frost damage. The pruning is a bit of a shock to the plant and it takes a week or two to get back in growth mode. The risk of late pruning is weather that does not permit you to get into the field, and bud break starts before pruning is complete. Early buds break off very easily, so pruning during bud break will cost you a lot of canes, and clusters.
The other benefit, if you are pruning late, is that the vines are beginning to grow. So, when you make a cut, a small amount of water will ooze out of the wood, thus pushing out any disease from one plant to another that could be spread thru infected pruning shears.
Early Pruning
With early pruning, you lose the benefit of delayed bud break, but you improve your chances of completing pruning before buds break out. You try to control the passing of diseases by sanitizing the shears at the end of every row and trust your frost protection system will prevent freeze damage, if needed. We use water, dousing the emerging buds with water as the temperatures get to freezing causes a tiny little igloo effect that protects the vines to about 28F degrees. We have not had to use our frost protection system for several years, and have a pretty clean vineyard from diseases, so we have been pruning earlier and earlier every year.
Fortunately, we managed to prune the entire vineyard before any of the super wet rainy season began. As you can see below, we are already seeing the tease of bud-break here at the end of January.
Cheers to the start of another great season!
-Steve Cass