A. Tree experts recommend only pruning away dead, diseased, or damaged branches which are crossing other branches or rubbing against each other because this will improve the structure and health of the tree. If you have to remove whole branches, it is best to cut them back to 'branch unions,' which are slightly raised knuckles on either side of the trunk where the branches join it. This will ensure that there is no damage to the tree. It also allows several large wounds to heal over and allows live wood to continue growing so that eventually strong callous forms across the wound and seals it up nicely. With shrubs, it is generally recommended to cut them back by no more than a third of their length, as this will promote new growth.