Evergreen refers to a group of plants that retain their foliage during winter. Most evergreens have a strong central branch leader, which requires little pruning except to control plant height, increase the density of branching, or to shear into special shapes.
Proper identification and growth habits are necessary before pruning or the natural shape and beauty of a plant can be destroyed. Evergreens can be grouped on the basis of whether they have whorled branches (pines, spruces, firs, and Douglas-fir) or random-branching patterns (yew, arborvitae, hemlock, cedar, and juniper). New growth extends from buds that were formed the previous year on the tips of twigs. However, a few random-branched species are capable of generating new growth on both old and new wood portions of the branch.
Prune all evergreens, except pine, before new growth starts in the spring or during the semidormant period in mid-summer. When pruning, follow the general branching pattern to maintain the natural shape. Remove dead, diseased, or broken branches anytime. When shearing, begin in late spring or early summer when new growth begins. This allows cuts to heal and new buds to form for next year. In most cases, selective pruning (one branch at a time) is better than shearing. Shearing creates a formal, geometric shape that looks out of place in a natural landscape and becomes more difficult to maintain as the plant increases in size. (Pruning paints are not necessary since pitch quickly seals the pruning wound.)
Occasionally, an evergreen may lose its leader. Sometimes a new leader develops from a latent (dormant) bud, or one of the uppermost branches will dominate and become the new leader. If no leader develops naturally, tie one of the topmost branches upright, training it to become the new leader. Shorten surrounding lateral branches to reduce competition.