Late Spring freezes are becoming more and more common, and it is important to take action to prevent damage to your buds.
A practice called double pruning can help avoid spring frost injury. Double pruning involves pruning the canes to 2-3x the desired amount of buds during the winter, which delays budbreak (and the risk of frost damage) by several days for the buds near the base of the cane. Then, after assessing cold injury and adjusting bud number accordingly, go through and prune to the desired number of buds shortly after bud break. It is important to remember that the act of pruning encourages bud development. Therefore, prune your most cold tender varieties later in the Spring than your cold hardy varieties.
For details on assessing bud damage, see the following videos:
Part I- https://www.youtube.com/watch?v=_RHJ5mY3fAs
Part II- https://www.youtube.com/watch?v=eWtr0jzI2Dk
If you do experience bud damage, take the following action to achieve desired yields:
0-15% dead primary buds- Prune normally
15-35% dead primary buds- Increase the number of buds retained by 35%
25-50% dead primary buds- Increase the number of buds retained by 50%
>50% bud damage- Minimally prune
For more information:
Frost Injury, Frost Avoidance, and Frost Protection in the Vineyard