Properly Trimming or pruning a tree is a delicate balance between tree health and aesthetics. knowledge in tree and plant biology as well as proper branch structure and pruning techniques is of the utmost importance for any one you plan on hiring to maintain your trees! NEVER hire a "tree trimmer" who is willing to "top" your trees! He doesn't care about you or your trees, he just wants your hard earned money! Topping is an unacceptable practice by the ISA and ANY competent arborist! Tree topping prohibits the trees ability to "feed" itself much like if someone were to sew your mouth closed! Topping will decrease the safety and lifespan of your tree substantially. It will be necessary to remove your tree much sooner than if it was properly pruned.