The best time to prune most trees and shrubs is in the late winter or early spring. Flowering shrubs should be pruned in late spring, after the plant is finished blooming.
Most trees and shrubs are best pruned just before they begin growing again. When a tree is dormant, it is easier see which branches need to be cut. Pruning flowering shrubs too early in the season prevents the development of flower buds, and the shrub may not bloom. Trim pines in mid-June, when the candles grow long, and trim spruce trees in the beginning of July. Dead, diseased or broken branches can be trimmed at any time of the year.