Evergreen trees such as spruce, fir, holly, pine, and southern magnolia can grow to great heights in the wild. They usually remain smaller in a garden, but may still grow too tall for the average home landscape unless pruned to restrict their size. These trees can be allowed to grow unhindered in a large open space; if planted close to a building or another tree, they must be pruned to control their growth.
Prune during the dormant season to restrict the size of an evergreen tree. Thin the longest branches to side branches using hand pruners or loppers. If necessary, use an extension pole to reach overhead branches.
Special Requirements of Needled Evergreens
Needled evergreens consist of pines, whose needles are arranged in bundles of 2, 8, or 5, and single- needled types, whose needles are not grouped but line the stems individually. These two kinds of needled evergreens have slightly different growth patterns and pruning needs.
Pruning Pines
The new growth of pines trees is called a candle. The candle is a new stem lined with buds and needles that expands during the growing season. Yearly pruning of pines can be limited to cutting back the candle growth partway. Heading a new candle forces the tree to develop terminal and lateral buds in a cluster at the ends of each cut; these buds grow the next year. Continual pinching or cutting back of the candles produces a densely branched tree. Be sure to prune before the stems of the new candles harden.
Scotch pine hardens late and allows more leeway; white pine hardens early and the stems may die back if not pruned in time. When pruning the terminal candles on pines, don’t cut straight across; slant the cut at a 45° angle. This angling minimizes the possibility of double leaders forming just below the cut, because a new bud will form at the farthest tip of the cut.
When only a portion of new growth is removed each year, large-growing trees will continue to increase in height and width. Eventually a pine can grow beyond its usefulness in the garden. To forestall this, thin long branches to side branches. This probably will eliminate new growth from a main branch, while allowing side branches to continue growing normally. Thin the main trunk this way to restrict the tree’s size; a lateral branch will take over as the new leader.
A less drastic measure calls for thinning into two-year-old wood early in the spring; new terminal buds will develop and grow the following season. Red, Austrian, and Scotch pines can be depended upon to produce new terminals when thinned in this manner.
Most conifers produce prominent branch collars. If a large living or dead limb must be removed, be sure to cut it off just to the outside of the collar; do not cut into the collar because the wound may not close over.
Pines produce a whorl of new growth each year, so age can be determined by counting the whorls of branches. Do not cut into wood older than two years, since it will not resprout. Pruning in spring into one- or two-year-old wood can control size without hurting the tree’s appearance.
Pruning Single-Needled Evergreens
Spruce, fir, hemlock, Douglas fir, and other coniferous trees with short, single needles, grow large just as pines do. Keeping them small by pruning is a continual task of pinching or cutting back new growth each year. For natural-looking results use hand pruners, not hedge shears. As with pines, single-needled conifers seldom resprout from old wood. New growth on these conifers emerges each year primarily from one-year-old buds of the previous season’s growth. The growth produces a whorl of side branches just below the leader.
Sometimes these conifers grow so rapidly that gaps develop between the whorls of branch layers. Prevent this disfiguring problem by shortening the leader each spring. Just beneath the cut, new terminal and lateral buds will develop into short stems and eventually into branches. Cut leaders approximately by half to a visible side bud or side shoot. Rub off any additional terminal buds to discourage multiple leaders from forming. If necessary cut back lower side branches to a bud or shoot to maintain a pyramidal taper.
Single-needled conifers permit a more flexible pruning schedule than do pines. Prune anytime from late summer, after growth has hardened, to just before new growth begins in spring.
Rejuvenating Old Needled Evergeens
Most overgrown conifers are difficult to renew because dormant and latent buds are viable for only a few years. Adventitious buds seldom form. One way to reduce overall size of pine, spruce, arborvitae, yew, and juniper trees involves drop crotching. Drop crotching is the practice of cutting a leader or main branch back to a major crotch to shorten it.
Start pruning at the top of the tree and work downward and around. Prune side branches back to a side whorl and shorten upper branches more than lower branches to maintain the conical outline. Expect the tree to take three to five years to recover from this drastic pruning. New growth will emerge from the existing terminal buds on the lateral branches; a side branch will eventually become the new central leader. Unless the tree is healthy and vital to the landscape design, it may be better to replace the tree entirely.
Regular thinning and pruning while an evergreen is developing and maturing keeps it compact and dense. Avoid ever having to rejuvenate or remove an overgrown evergreen tree by properly controlling its growth from an early age.