Pruning of ash trees should be done in the late dormant season. The pruning should be done in the late winter before the spring growth begins. Pruning in this manner leaves fresh wounds for only a short amount of time before the new growth can start the healing process.
Pruning ash trees is done to maintain the plant, improve its appearance, and to protect people and property from falling branches. Pruning should begin when the tree is young to create a strong structure. Four common types of tree pruning for a larger ash tree include, crown thinning, crown raising, crown reduction and crown cleaning.