Crown thinning is the removal of small diameter branches (including, dead dying and crossing branches). This method does not alter the overall size or shape of the tree, it is simply performed to lesson the trees foliage density. This procedure is effective for increasing day light penetration and to reduce damage that could result from crown resistance against strong winds.
Crown thinning is effectively pruning the tree to reduce size safely. Reducing the size of the canopy also means less weight and a greater resistance to high winds. It also enables light to penetrate beneath the canopy encouraging growth of neighboring plants and bringing more light into neighboring homes and gardens. Crown thinning is not to be confused with canopy reduction. Canopy reduction is the process in which larger branches are strategically removed. Crown thinning is the process of removing the small dead branches that have grown ungainly.
In most cases the thinning is best performed in late summer when tree healing is most effective or in winter when the trees are dormant and branches can be easily targeted. Typically thinning removes around 30% of the canopy with careful pruning.