Over time, continued over pruning may lead to branches that are too weak to tolerate wind or ice loads, or the plant may simply exhaust itself trying to replenish its canopy. ... So, although pruning may not kill your plant directly, over pruned trees and shrubs can die as a long term result of the associated stress.

Can you cut back trees in the summer?

Pruning prevents disease

Pruning in summer helps to avoid infection, as the fungal spores are airborne between September and May. This is also the time to prune out any branches that are weak, competing or crossing. Discover how to prune plants to avoid disease.

What happens if you prune trees in the summer?

Pruning during the growing season always stimulates new growth. During summer's heat, having to produce that ill-timed new flush of growth greatly stresses a tree. Pruning in the fall is even worse as it prevents the tree from going into a natural dormancy. The exception is heavily damaged, disease or dead wood.