The most common system used by Arborists is natural pruning. The goal is for the tree to remain in a more or less natural state while allowing for the tree's unique growth pattern and adaptations. There may also be alterations for clearance, view, aesthetics and structural improvement. Overall general shape of tree is not altered in a major way, most Arborists would prefer that is a tree is pruned in a natural system.
Reduction pruning refers to reducing the crown or canopy size of a tree. A typical reduction is measured by reducing the percentage of the canopy by 1/3, 1/4 or 1/2. This is best accomplished by reducing limbs back to their point of origin or back to laterals capable of sustaining the remaining limb.
Clearance pruning encompasses several methods.
Pollarding, Espalier and Topiary are specialized forms of pruning.
The goal is not to be aesthetically pleasing but rather to create a strong fruit-bearing structure that provides room for sunshine, air circulation and fruit production. Long term strategy rather than a one time job and timing of the year is very important. As a rule, growth is maximized if pruning is done just before the buds swell, in the late winter or early spring. Pruning when trees are dominant can minimize the risk of pest problems associated with wound entry and allow trees to take advantage of the full growing season. Best time of the year for pruning is mid December through March.
Vista pruning is a style used to enhance a specific view.