When people want to reduce the size of a tree they most commonly think of ‘topping.’ Unfortunately, ‘topping’ (the cutting of main branches back to stubs) is perhaps the most harmful tree pruning practice known.
There are many reasons why people decide to reduce the size of their trees. People often feel that their trees have become too large for their property. They may want to let light and views into their property, to clear utility lines or the trees size may pose a hazard.

Topping, however, is not a viable method of height or size reduction and certainly does not reduce any hazards. In fact, topping will make a tree more hazardous in the long term.

Hazards caused by topping

Topping encourages the growth of many weakly-attached branches that are high and likely to break. Topping cuts often create stubs with wounds that the tree may not be able to close, leaving the exposed wood tissues open to decay and insect invasion.
Topping also suddenly exposes the remaining branches and trunk to high levels of light and heat. This can cause sunburn of the tissues beneath the bark, which can lead to cankers, bark splitting, and death of some branches.

The healthy way to top a tree

There are recommended arboricultural techniques to reduce the height or spread of a tree. Known as crown reduction, branches can be removed back to their point of origin or cut back to a lateral that is large enough to assume the terminal role. This method of branch reduction helps to preserve the natural form of the tree.

Crown reduction reduces the trees size and maintains its shape and strength.

Trees form a variety of shapes and growth habits, all with the same goal of presenting their leaves to the sun. Topping weakens the tree, destroys its natural form and increases the need for future pruning. In contrast trees that have been reduced properly will maintain their structural integrity and form and the frequency of future pruning is reduced.