Pruning: Addition By Subtraction

By Gil Medeiros, former Fairfax Master Gardener
Something amazing happens when we clip the growing bud at the tip of a branch. This simple act initiates chemical processes within the plant that cause other buds further down the branch to grow into lateral branches. Some of these buds — called lateral or axillary buds — are located where leaves attach to branches. Others, called latent buds, are hiding under the bark of woody shrubs and trees. The science of pruning is based largely on this single phenomenon of plant physiology.

terminal bud

Terminal bud exerts apical dominance on lateral buds

The phenomenon is called apical dominance. Apical refers to the apex or highest point on the branch. The bud at the end of the branch is known as the terminal bud. It exerts apical dominance; in other words, this bud controls growth of other buds lower down the branch. When it is healthy and intact, the terminal bud controls that growth by releasing chemical growth-inhibitors called hormones. These chemicals flow by gravity in plant sap to adjacent buds. Removing the terminal bud disrupts the apical dominance effect on that branch, allowing other buds to grow until another bud takes its place.

Apical dominance allows a plant to concentrate its growth resources on the main shoot growing from the bud at the top of the tree or at the end of a branch. This key process helps the plant grow tall to compete with other plants for sunlight.

So what?

There are three