Pruning is the process of selectively removing branches from a tree to remove unwanted growth, improve the trees structure, and direct new, healthy growth. It is done to improve the overall health, strength, and appearance of the tree or shrub. Pruning can be used to remove dead, diseased, or damaged branches, as well as to shape and thin out the plant. It can also be used to stimulate fruit production and increase the value of timber. Pruning for safety involves removing branches that could fall and cause injury or property damage, trimming branches that interfere with lines of sight on streets or driveways, and removing branches that grow into utility lines. Pruning for health involves removing diseased or insect-infested wood, thinning the crown to increase airflow and reduce some pest problems, and removing crossing and rubbing branches. Pruning can also be used to encourage trees to develop a strong structure and reduce the likelihood of damage during severe weather.

Tree trimming, on the other hand, is the process of removing tree parts for reasons other than the health of the tree. Trimming is usually done to improve the trees appearance and functionality within the landscape. It is most often used to maintain the overall size or shape of a tree or shrub or to increase light to the lawn. Trimming mostly involves thinning out overgrown branches, which helps create shapely growth.

In summary, pruning is done to improve the health, strength, and appearance of a tree, while trimming is done to improve the trees appearance and functionality within the landscape.