Tree pruning or crowning helps trees to grow stronger and look more attractive. The reason one prunes a tree is to remove damaged or dead branches which allows for new growth but can also be done to produce a distinctive shape. Also when one decides to crown or prune a tree the time of year becomes a factor. If your goal is to help a tree grow then pruning in the winter will cause large amount of growth to happen in the spring. But if you already have a large tree that needs to be maintained and to slow the growth process then choosing the summertime would be a better option.