We value trees for the shade they provide, the fruit they produce and the beauty they add to our yards and parks. The United States Department of Agriculture website states, "The main reasons for pruning ornamental and shade trees include safety, health and aesthetics." Different trees need slightly different types of pruning, but the basics are the same for all trees.
Trimming for Safety
When a tree grows in an area where humans, animals, buildings or vehicles often exist under or near the tree, it's wise to keep the lower branches trimmed back so they do not impede access. Also, fruit trees can drop overripe fruit where it can make a mess or even injure people, animals or property. Trimming higher branches can also open up the ability to better see a street or driveway. If you keep trees trimmed back from your home's entry doors and windows, burglars will be denied hiding places and cover. You'll also want to keep your trees trimmed back from power and telephone lines.
Trimming for Tree Health
When you prune any tree, the first thing to look for is dead and broken branches and those that bump into each other. When you trim extra branches you open up airflow through the tree---doing this will cause certain fungal diseases to be less likely to strike. Always trim all growth that is infested with disease or insects. The Department of Agriculture advises, "Pruning can best be used to encourage trees to develop a strong structure and reduce the likelihood of damage during severe weather."
Trimming for Tree Aesthetics
You can trim many types of trees to the shape and size you desire to keep them small enough to fit well into your environment and to facilitate your harvesting of fruit. When you trim a tree for aesthetic purposes, you "enhance the natural form," according to the Department of Agriculture. You can also help to stimulate flower or fruit production if you trim a tree for form.
When to Trim Your Tree
Prune most deciduous trees during their winter dormant season. Be sure to do a little research on the type of tree you want to prune because certain trees, such as the fruitless mulberry, require a drastic type of trimming called pollarding, where you cut all branches back to the main trunk. This type of severe pruning is not appropriate for fruit trees and many flowering or shade trees. You can prune citrus trees at any time of year, but be sure not to cut off any flowers or immature fruit unless the tree has a serious infestation of insects or disease.
Cautions and Tips
Tree trimming can be a big job if your tree is large. It might require you to climb a ladder and use a chain saw. Consider hiring a professional arborist or tree service for large jobs that can present hazards to inexperienced gardeners. When you prune any tree, cut branches back to the main trunk, but avoid cutting into the "branch collar," which is a knobby, raised area where the branch connects to the trunk. Pruning tar is not necessary---many experts warn that applying this type of product can seal in moisture, microbes or insects, which will adversely affect your tree's future health.