The standard advice is to prune spring flowering shrubs right after flowering and to prune summer flowering shrubs in winter or early spring. Is this the best advice?
Shrubs respond to pruning differently depending on when it is done. Pruning during dormancy (i.e. late fall to early spring) removes dormant leaf buds and may also remove dormant flower buds. Pruning during dormancy does not cause the shrub to initiate new growth.
Pruning in mid or late spring after flowering has a different effect. Pruning removes newly formed leaves in addition to wood. The shrub has just grown the leaves and in many cases they are not yet fully developed. The process of growing these leaves requires significant food reserves – food that was stored the previous year. The leaves have not yet paid the shrub back for using these food reserves.
The shrub’s reaction to losing leaves is to activate more dormant buds and many shrubs tend to over react by activating too many buds. This drains even more of the food reserve and weakens the shrub by depleting extra food reserves. Most shrubs will survive this situation, but it is not really the best thing for the shrub.
Too many activated buds leads to too many branches, and increases the need for future pruning which is not good for the shrub and more work for you.
The advice to prune spring flowering shrubs after flowering is good for flower production, but it is not the best advice for the health of the shrub. The best time to prune these shrubs is also during dormancy. So you need to decide; are you willing to miss a years worth of blooms for the health of your shrub?
Fall Pruning – What is It?
Common advice suggests that you should not prune shrubs in late fall. This type of pruning, in colder climates, results in new growth that can’t harden off before winter. The result is severe winter damage.
Is this true? For insight into this topic have a look at Best Time to Prune Trees and Shrubs.