In general, trees can be trimmed at any time of the year, but unless there is an overpowering reason, it’s often best to do so at the end of winter and before the spring growth. Trimming at this time of the year actually encourages new growth, so if a tree isn’t doing so well, talk to our arborist about a little light trimming to give it a boost. It’s also better to trim deciduous trees in late winter when they have dropped their leaves because it’s easier to see the branches and where they need to be trimmed.
On the other hand, if you want to limit a tree’s growth, because it’s getting out of hand, trimming back the branches during summer is often a good strategy. You must be careful, however, not to take too much off the branches during summer, because this can cause the tree to become stressed and ultimately, unhealthy. Growth following a summer trimming will be less vigorous than during late winter, which might just solve your problem if the tree is taking over your garden.