Tree Trimming Basics: Topping Versus Crown Reduction

Tree topping, sometimes called heading, creates a flat-topped tree because all of the vertical branches are removed in order to reduce the height of the tree.

The method is straightforward: cut off all the lateral branches above a certain height so that the canopy isn't too tall. Sometimes, the lateral branches are also cut back to a prescribed length to further control the canopy.

Topped trees have an obvious flat top that many people find unattractive. In some cases, only part of the canopy may get topped, such as only on the side that has grown into the power lines.

A topped tree has an unnatural form that can lead to several health and structural concerns. Scrubby, weak growth can result along topped branches as the tree tries to recover the lost foliage.

Topped trees can also collect heavy snow or ice loads in winter, which increases the chances of branch breakage or trunk splitting. Sun damage due to a too-thin canopy and insect infestations can also plague topped trees.

You only have a few reasons to top a tree, since the negatives far outweigh any positives. The only exceptions are trees that can be trimmed into formal hedges, such as some evergreen trees. Even then, a slightly rounded or sloped top is preferred to a flat top that collects snow and moisture.

Further, when topping formally pruned shrubs, ensure the bottom is wider than the top so sun and moisture can reach the lower branches.

Crown reduction takes a more cautious approach than topping. Branches are selectively cut to reduce the overall size and density of the canopy.

Crown reduction methods require assessing the length, position, and health of every main lateral and vertical branch in the canopy. Branches are then selectively cut back, typically by no more than a third of their length, to help control the shape and size of the canopy. Cuts are made near buds so that the ends of the branches leaf out, which helps prevent sun-scald on the newly cut branch tips.

Some interior branches are also removed to help open up the canopy so sunlight can filter in and to allow for air circulation. Generally crowded branches and those that are weak or damaged are chosen for interior reduction pruning.

Most concerns center on how well the species of tree reacts to extensive pruning. Some species are more prone to rot or stress from cutting. Your tree service can alert you to which species shouldn't be extensively pruned in your area.

Trees can recover in a season or two from reduction pruning, so this type of pruning is an ongoing process that must be completed annually for the life of the tree.

Consider crown reduction for any tree that can handle extensive pruning and that has grown larger than desired. Mature trees can benefit from reduction pruning, but the best method is to start when the tree is still young. The younger the tree when you begin reduction pruning, the fewer cuts that will need to be made as the tree matures since the canopy won't have a chance to become overgrown.

The best way to manage tree height is two-fold: create an annual pruning plan and stick to it, and only plant tree varieties with mature sizes that fit the planting site. If you do need to consider topping or crown reduction, contact a professional service like Baumann Tree for help.