Pruning established trees

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Reducing the length of or thinning weak or poorly attached branches, branches that are overextended and too long, or the longest branches in the crown will minimize the likelihood of failure and improve tree architecture. In many cases on large trees it is better to reduce the length of branches than to remove them in order to preserve health.

Here is why: 1) Shortening the largest branches reduces likelihood of tree failure by reducing the wind force on the canopy. 2) Reducing branch length or thinning branch ends can help keep them from drooping. Drooping branches in the lower crown often need to be removed later because they can get in the way. Removing large branches from the trunk can initiate decay and cracks in the trunk which can cause tree failure later.

Reducing the canopy height using appropriate reduction cuts on trees with most of the foliage at the top of the canopy will reduce the likelihood of the tree falling in storms. Reducing the size of the canopy is accomplished at the expense of tree size and the accompanying benefits.

A community filled with small trees will not benefit from the bounty provided by large canopy trees. Benefits from large canopy trees include energy savings in some cases, reduced rain runoff, increased real estate value, less soil erosion, increased well-being, reduced crime, and increased spending at retail stores that are nearby.

Thinning the canopy on full canopied trees can also reduce wind load and likelihood of failure.

Removing dead branches from the tree canopy will reduce the likelihood of people getting injured from falling branches. This can also help keep the tree in a high-energy, healthy status by maintaining sapwood in a functioning state. If some small dead branches (less than 1.5 inches diameter) are left in the canopy, birds such as woodpeckers may be more visible in your landscape.

Elevating the bottom portion of the canopy will increase sunlight penetration to turfgrass and other plants under the canopy. Tree health can decline from removing too many low branches at one time or from removing large branches. Living cells in wood on the interior of the tree can die or decay as a result of over pruning.

Elevating too much can also shift too much weight toward the edge of the canopy which can increase storm damage. To preserve tree health when elevating the canopy, consider reducing the length of large branches using reduction cuts instead of removing them entirely. Reduced major branches can often be left on the tree for a very long time, whereas major branches with small interior and lower branches removed often droop and get in the way. This requires their removal later leaving a huge pruning wound.

Because of the potential for massive decay on certain tree species, remove branches greater than about 8 inches only after all other options have been considered. Ideally, elevate the canopy by removing every other branch now and the rest of the low branches a couple years from now.

By waiting, you might find that the rest of the low branches do not need to be removed after all. When the canopy is elevated or raised, consider reducing the length of long branches in the upper canopy. This combination will help minimize likelihood of the wind catching the canopy.

Removing low branches that are close to or resting on your roof will reduce building damage. Follow the guidelines outlined above.