This is where the crown of the tree is reduced in size, either the entire crown or in a specific area to redress an imbalance of the shape of the crown. To reduce stress and large wounds no more the 30% of the overall crown should be removed in one year, and the out-come should be to leave the tree looking as natural as possible and not to leave  thick, cut branch ends on the externals of the crown. A good crown reduction will leave the tree with a strong framework of large branches, which support plenty of smaller branches and twigs (leaf bearing material) capable of producing dense leaf coverage next season.

When to perform a crown reduction:

When a tree has outgrown its position, but removal of the tree is undesirable.

When a trees stability is in question due to defects or movement in the ground.

To aid in the re-balancing of the crown.

To maintain a desired crown shape.

When not to perform a crown reduction:

Certain tree species do not react well to crown reductions, such as Conifers which in general often look poor afterwards, and Maples which will re-grow vigorously put and become overly dense due to this growth.

When a tree is obviously the wrong tree for its position, it may be best to remove it and start again with a more suitable tree.