Pruning is necessary for maintaining a mature tree.
- Cleaning is the removal of dead, dying, diseased, weakly attached, and low-vigor branches from the crown of a tree.
- Raising removes the lower branches from a tree to provide clearance for buildings, vehicles, pedestrians, and vistas.
- Reduction reduces the size of a tree, often for utility line clearance. Reducing a tree’s height or spread is best accomplished by pruning back the leaders and branch terminals to secondary branches that are large enough to assume the terminal roles (at least one-third the diameter of the cut stem). Compared to topping, reduction helps maintain the tree’s form and structural integrity.
- Reducing density of foliage at the crown periphery, thinning, is sometimes performed to increase wind or light penetration for aesthetic reasons and to promote interior foliage development.