As they mature, many trees and shrubs need some pruning to encourage pleasing, healthy form. Pruning encourages flower and fruit production and allows more light and air to reach the inner branches. When pruning, always use sharp, clean tools, and prune at the correct time during the year. Here are some guidelines. Spring-flowering shrubs such as lilac (Syringa), viburnum (Viburnum), and forsythia (Forsythia) should be pruned right after they bloom. Summer-flowering shrubs such as butterfly bush (Buddleia), beautyberry (Callicarpa), and crape myrtle (Lagerstroemia) should be pruned in early spring before new growth begins. Remove branches to achieve a desirable shape. Prune evergreen shrubs after new growth begins. Prune mugo pines only in the candle stage (while the new shoots are elongating). Prune shrubby spruces, junipers, and yews just after new growth begins through midsummer. Boxwoods can be pruned in late spring and early summer, especially if you are training them into topiary shapes.