Gordon Johnson, Extension Vegetable & Fruit Specialist;gcjohn@udel.edu
The effects of winter injury on grapes is now very evident. Affected grape vines are delayed in leafing out, have week shoots or limited shoots, and in severe cases, have been killed down to the graft union.
We have a research and teaching vineyard at our University of Delaware Thurmond Adams Research Farm near Georgetown Delaware where we have plantings of vinifera and Hybrid Wine grapes and table grapes (American background). There is little or no injury on the table grapes and hybrid wine grapes. However, vinifera wine grapes have significant injury on certain varieties. Most noticeable is damage on year old canes from the plant base, where most buds were injured.
Pictures illustrating the damage are shown below.
Vinifera vine with normal shoots
Vinifera vine with some reduction in shoots
Vinifera vines that have not budded out and are dead to the graft union
Vinifera vine with week and sparse shoots
Hybrid wine grape with normal growth
American table grapes with normal growth