During the first month of spring, I am commonly asked if it is too late to trim one's trees. The answer to that is no. Ideally, it is best to trim trees during the dormant season before the trees begin budding and leafing out. Doing this prevents the waste of any of the tree's resources and can minimize reactive growth. However if one follows common Arborist rules such as never removing more than 20% of the crown in any one trimming you can prevent the negative reactions to trimming even in months of extreme heat. Certain species such as silver maple may leak sap from cuts during summer months however this is just an aesthetic downside to trimming in the in late spring and summer.
In addition, I should mention that common trimming services such as corrective pruning, or crown cleaning focus on removing only unhealthy and detrimental growth from trees. These pruning practices focus on the removal of stub cuts/improper cuts, dead, broken, diseased, and crossing branches. The removal of this material is always a good practice regardless of the time of year.
