This bushiness eventually obscures the structure of shrubs, reduces flowering, and invites fungal disease. Periodic pruning makes them more attractive and healthier. Pruning to control size is a waste of time -- they will just grow back. Instead, guide them so they grow to their mature size with strong stems and healthy foliage.
Experienced gardeners usually do their major structural pruning when shrubs are dormant, then perform follow-up shaping during the growing season, after the spring growth spurt. Prune your flowering shrubs to shape them after they've bloomed and before they set buds for the following year, so you don't inadvertently remove the buds and ruin next year's bloom. Plan to shape spring bloomers, such as rhododendron, azalea, and forsythia, in early to mid-summer. Wait to shape summer bloomers, such as crape myrtle and glossy abelia, until autumn.
Clip branches individually, and reserve shearing for hedges. The idea is to groom the shrub to curb unruliness, not to change its appearance. Properly shaped, the shrub should look essentially the same, only neater.
Whether deciduous or evergreen, trees and shrubs have a dormant period. Except for certain tropical trees, this rest time is usually during the cold winter months. During the period when days are short and the ground is cold, they suspend active growth and live off stored energy. Warm weather triggers new vitality.
When shaping shrubs, achieve optimum results by honoring their natural habit. Use restraint. Respect the fact that each shrub is genetically programmed for a certain size, profile, and branching pattern. Make cuts that support these features and preserve the essential character of the plant. Lollipop shapes look unattractive on the front lawn. Leave the highly stylized pruning -- topiary, pollarding, and bonsai -- to the experts.