AusBonsai

Andrew Legg wrote: Pinching takes two forms. Removal of growing tips to stimulate back-budding, and removal of larger leaves, both forms of defoliation:

• Removal of growing tips is done to stimulate back-budding. The growing tips of branches are where auxins (a plant growth regulating chemical) are manufactured by the plant. Auxins suppress buds further back on the branch, and thus by removing the growing tip, and the related auxin production, buds further back are then 'activated' and begin to grow. A tree produces a specific amount of energy, some more growth equals more leaves. Divide the same energy by more leaves and you get smaller leaves.
  
  Removal of larger leaves means that the tree produces new leaves which are typically smaller in size as it has less energy to grow the new leaves.

Defoliation normally refers to the removal of leaves either in totality of partially usually for one of a few reasons:

• Damaged leaves can be removed to replace with healthy new leaves (something that can be done with wind damaged maples).
  
  Removal of some leaves allows more light into the tree and promotes formation/development of new buds deeper within the branch structure. Same applies to removal of all leaves.
  
  If an emergency repotting is done out of optimum season, sometimes partial of full leaf removal can be done to reduce transpiration during a time then roots are disturbed

So there you go . . . . those are the ones that spring to mind. Answer: Defoliation and pinching are very similar, but depending on what you want to achieve, they are used slightly differently. Evergreens and deciduous trees can respond differently to these practices, so do species specific research before embarking on any specific technique on a tree.

Cheers,

Andrew