When you trim your tree, you are effectively helping to maintain the tree’s appearance and shape. 

Sometimes you need to trim a tree to save it from a disease that it has. When you prune or trim away affected limbs and branches, it can help your tree live when it otherwise may have died. 

Triming is Vital to Hurricane Damage Prevention
A strong, deep-rooted tree may not fall during a storm, but weak limbs in the canopy may. Broken, dead and damaged limbs can be torn from trees during a storm and turned into dangerous projectiles.