Have you seen trees and shrubs turning brown or ashen gray on one side at the end of winter? You may be looking at winterburn. It's a condition that usually occurs on the south and southwest sides of needled and broadleaf evergreens when winter sunshine heats one side of the plant above the ambient temperature and wrecks havoc on the plant's internal moisture system. The problem is not necessarily fatal once it has occurred, but prevention is better than dealing with it after the fact. Prevention begins with proper moisture and root care in the prior summer, according to arborist Jeremiah Green at The Care of Trees in Hamden and Norwalk.