The best time to prune your tree is when the tree is dormant, which is in late autumn or winter. The reason for this is explained below:
Phenology
This is the timing of a natural process, trees have major periods within this process, and these are as follows:
Period 1 Intense utilization of an available energy source
Period 2 Rapid reproduction
Period 3 Movement of new individuals to new potential growth sites
Period 4 Dormancy
There are two critical periods within a trees potential energy these are:
Period 2 – When the leaves have completed formation and Just before dormancy when energy reserves are at their lowest.
It is important that a tree is not pruned when its energy reserves are low as it can cause undue stress and even death!