Correct pruning is part science, part art. The science comes into play when you begin to understand how plants grow and respond to different pruning cuts. Understanding this response helps the gardener develop a good sense about how, where, and when to make a pruning cut. The art comes into play as you shape a plant — deciding which branches to remove and which to leave intact, which to shorten, and which to allow to grow. The result is a tree or shrub that grows into the shape envisioned in the mind’s eye — a shape that suits the plant and looks appropriate in the garden setting.
In the same way that the artistic side of pruning changes as tastes and preferred landscape styles change, so does the scientific side of pruning evolve with new discoveries. Pruning techniques employed today are different from — and better than — those used 10 years ago because of recent discoveries about how woody plants respond to pruning wounds. And these important changes in technique mean healthier, longer-lived trees and shrubs. Improper pruning can actually harm valuable trees.