Why do some of my trees and shrubs suffer winterkill some winters and not others?
Winterkill is caused by dehydration during the winter months — the plants don’t get adequate water. You can take steps to prevent this, including giving your shrubs and trees a final watering after the first frost but before the ground freezes hard. Water them twice — about two weeks apart. The soil should be soaked to a depth of about 18 inches.