Crown thinning is the removal of branches to produce a even density of foliage and an regular branch structure.
It is usually confined to broad-leaved species and does not alter the overall size or shape of the tree.
Branches should be pruned systematically throughout the tree, should not exceed the stated percentage of no more than 30%.
Common reasons for crown thinning are to allow more light to pass through the tree, reduce wind resistance and reduce weight.
Thinning is preferable to crown reducing as less reactive growth should be produced by the tree and the natural tree form will be retained so presuming the tree has been chosen well for it’s location then the maximum size for that species should be acceptable.
Fruit trees will benefit from cleaning the crown of thick clumps of interior growth, improving crop and discouraging fungal attacks.