The Objective of Structural Pruning.
Young trees should be pruned to guide growth so their crowns clear traffic, signs, and buildings while ensuring that they develop strong structure. Established trees in urban landscapes should be pruned primarily to reduce risk, preserve a tree structure that boosts amenity values, provide clearance, and improve the aesthetic value of the property. Achieving these customer expectations requires different pruning strategies for trees of different species, life stages, and size at maturity.
Pruning Dose: How much is enough?
The answer is that it depends on the pruning objectives and the severity of the defects. The pruning does is the estimated percentage of foliage of bud removed during pruning compared with the total amount on the tree prior to pruning. The ANSI A300 Part I. Pruning standards, 6.1.4 states that "Not more than 25 percent of the foliage should be removed within an annual growing season. The percentage and distribution of foliage to be removed shall be adjusted according to the plant's species, age, health and site."