5 Steps of Structural Tree Pruning

If you don’t know what you’re doing with tree pruning, don’t just start hacking at your trees. Not only will they look bad, but you’ll undoubtedly damage them as well. A certified arborist knows how to prune your trees the right way, using the following five steps:

Step 1: Remove broken, dead, dying, or damaged branches.

Self-explanatory, yes? 

Step 2: Select and establish a desired structure, most often a dominant leader.

On most trees there should only be one leader, which is usually the strongest, most vertical stem. Competing stems should be subordinated (reduced to become laterals) or removed. If two branches develop from apical buds at the tip of the stem, they will form codominant stems. Each codominant stem is a direct extension of the trunk. It is best to remove one codominant stem when the tree is young. 

Branches that have very narrow angles of attachment and codominant stems tend to break at the point of attachment, especially if there is included bark. Included bars is bark that becomes enclosed inside the crotch as the two branches grow and develop. This weakens the branch attachment, making it more likely to split apart.

The relative size of a branch in relation to the trunk is more important for strength of branch attachment than is the angle of attachment.

Step 3: Select and establish the lowest permanent branch.

The height of this branch is determined by the location and intended function of the tree. For example, the lowest permanent branch on a street tree should be higher than that on an arboretum specimen. The lowest permanent branch should be less than half the diameter of the trunk at the point of attachment.

Step 4: Select and establish scaffold branches.

These branches should be selected for good attachment, appropriate size, and desirable spacing in relation to other branches. Scaffold branches should be well spaced, both vertically and radially, on the trunk. As a guideline, vertical spacing should be at least 18 inches for large-growing trees, and about 12 inches for smaller trees.

Step 5: Select and subordinate temporary branches below the lowest permanent branch and among the scaffold branches.

These branches should be retained temporarily because they help provide energy to the trunk, contribute to trunk taper development, and provide shade to the young trunk tissues. The smaller temporary branches can be left intact; larger ones should be subordinated. The temporary branches are removed in later years. This training process of tree pruning should be spread out over many years. The goal of tree pruning should be to remove more more than 25 percent of the canopy in any one year. And keep in mind that professional tree pruning should start when your trees are young. In young trees, defects can be removed; a single, dominant leader can be selected; and branches can be well spaced along the main trunk. Trees that are structurally pruned when young should have fewer structural defects (such as codominant stems), which means they also have less potential for failure at maturity. They also tend to require less maintenance as they age.