Pruning our trees can be very beneficial to them, but it can also be very damaging. All pruning wounds the tree, and the tree has to respond to the wound by trying to seal away the damaged area so that decay fungi cannot get at the interior wood. Smaller cuts seal more easily; larger cuts may never seal in time to prevent the onset of decay. Pruning also take away leaf tissue, and that limits how many sugars the tree can make to feed itself (through photosynthesis). Pruning too heavily can lead the tree into a starvation cycle. So – have a good reason before pruning!