Shrub Pruning in Summer
Recommendations for pruning flowering shrubs always suggest doing this work in the dormant season, often from late winter into early spring. But what if the weather or other priorities discourage outside work at those times? It often means that shrubs are not pruned until after most have flowered. Well, don’t be discouraged; shrubs can be pruned during the warm summer months. It won’t kill the plants.
Pruning in the summer is best done as soon as possible after flowering, to favor as many of next year’s flower buds as possible. The later into the summer pruning is done, the more gentle it should be, in order to preserve as many flower buds as possible, and to limit the probability of winter injury on new growth that might not be adequately hardened off.
The worst that can usually happen is that flowers are lost for a growing season. Winter injury often depends as much on species susceptibility to cold as it does the timing of pruning, and winter injury does not often kill entire, established plants.
The same principles apply to sheared hedge shrubs. Shearing is usually undesirable for a variety of reasons, not the least of which is that late-season shearing tends to encourage tender new growth that will not have time to harden off. The winter injury that might result is rarely fatal to the entire plant, however.
If your shrubs really need the pruning, it might be better to do it in summer than not at all, and accept the small risks that entails.