Grapevines are in various stages of early growth throughout Indiana, ranging from bud swell to 6-8 in shoot growth, depending on variety. A cold weather event came across the state on 4/24 bringing temperatures as low as 25°F (see Figure 1).
The minimum temperatures in the following areas were reported as follows:
Lafayette, IN: 28.9°F
Spencer, IN: 27.0°F
Vincennes, IN: 29.8°F
Figure 1. Midwest Regional Climate Center
Figure 2. Frost damage on grapevine shoot at Meigs Horticulture Research Center in Lafayette, IN after low temperature of 28.9°F on April 24, 2023
Freeze damage April 24 2023 SWPAC
Preventing Frost Damage:
Delayed pruning: The act of pruning encourages bud development. Therefore, delay pruning until late April/early May until much of the risk of frost has passed. Also, prune your most cold tender varieties later than your cold hardy varieties.
Double pruning: Double pruning involves pruning the canes to 2-3x the desired amount of buds during the winter, which delays bud break (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.
Resources for Assessing the Extent of Injury:
Guide to Assess Freeze Damage of Grapevines | The Ohio State University
Prevention and Management of Frost Injury in Wine Grapes | NC State Extension