With the exception of evergreens, shrubs used for hedges are pruned almost any time of year. The best time depends on the type of shrub. To help determine the best time to prune, find out as much as you can about your plants.
Prune narrow-leaved evergreens with small needles, such as junipers and taxus, in spring before growth starts. Prune narrow-leaved evergreens with large or coarse needles, such as pine or spruce, in spring after growth starts. Broad-leaf evergreens, such as hollies, need an early spring pruning, then a lighter pruning later on to straighten the hedge line.
Prune fast-growing hedges as often as necessary, which means any time they add 6 to 8 inches of growth. Begin pruning in late spring. Prune slow-growing hedges once a year in late spring after the shrub has completed its annual growth.
Limit late summer pruning to avoid injuring the shrub. Pruning encourages new growth, and new growth late in the season doesn't have a chance to harden before freezing temperatures set in.