Cutting the top from a pine won't immediately kill the tree, but a large pruning wound could leave the tree open to potentially deadly infections. Canopies of pine trees and many other evergreens grow outward from the needle-bearing tips of branches. Cutting back a branch to the bare wood inside the green canopy kills the branch. Cutting out a pine's top stops vertical growth unless new leaders form.
Pine trees with top damage could survive if most of the canopy escaped injury. Cutting back the damage to just above healthy limbs could save the tree. If the first possible clean cut removes most of the crown and leaves large limbs exposed, the pine cannot recover its natural shape. Direct sunlight shines into the tree's centre. Bark could sunburn and split, exposing the tree to more damage from disease and insects. If the damage only involves the very top of the pine, green growth near the trunk could gradually replace the top of the tree.
Small branches on either side of the broken leader could sprout new vertical shoots. Left for a few years, the multiple leaders gain height but develop branches only on their sunny sides and compete for light and space. If not trimmed out, the crowded leaders could fail under a load of heavy snow or ice. Cutting out all but one maturing leader leaves a top with unbalanced foliage. Early pruning prevents this unsightly growth. When new leaders reach only a few inches in height, cut out all but the strongest for the best chance of restoring the tree's natural pattern.
Creating New Leaders
If damage extends too far down the tree to allow natural leader replacement, bending a small branch upwards forces a replacement for the tree's top. Limbs of an inch or less in diameter bend easily. An upright wooden brace fixed to the side of the trunk provides a vertical guide for lashing the new leader in place. Tied to the brace for two years, the limb permanently takes on the new position. The scar on the old top forms a weak point at the base of the new leader. Insect damage or fungal infection could make the repair short-lived.
When the top of a pine tree suffers major damage, the best solution involves removing the tree and planting a replacement. Topping pine trees growing too close to power lines creates oddly shaped trees with bushy upper growth. Selecting a planting site that allows room for maximum growth without trimming gives pine trees the best chance for long life. In a good location, pine trees need little trimming. As the tree matures, lower limbs die back and require removal. Cutting out broken or diseased limbs improves the health and appearance of the tree, but pines develop beautiful symmetrical form without pruning.