Winter Trimming
Hello this is Green Goddess owner Matt Filla. As a general rule of thumb, late winter is the best season for pruning trees and shrubs. Main reasons for optimal pruning timing often occurring in February and early March are:
Extremely low to zero chance for plant pathogens to spread. Diseases prevented with winter pruning include Oak Wilt, Locust Cankers, and Apple Fireblight.
Tree surgeries waste less energy during winter dormant season. Less energy is distributed in the limbs plus there is no wasted foliage with deciduous tree limb removal. Spring trimming is usually the most stressful timing as trees with lower energy reserves after winter have pushed limited energy resources into the first flush of foliage.
Although early winter can be solid pruning timing, late winter is usually better as open limb cut wounds are less frequently damaged from winter cold snaps. This is because late winter is close to spring growing season when wounds have a chance to heal and the most severe cold snaps are already done.
Consult University of Minnesota Extension for more pruning tips:
Above is a link to the University of Minnesota Extension resource for more specific details. Notable species exceptions with late winter sap flow are Maple and Hackberry.