When Should You Prune?
Avoid pruning flowering shrubs in late summer or autumn as this can stimulate tender new growth which can be damaged by cold temperatures.
Knowing if your plant flowers on new or old wood helps you determine when it's the best time to prune.
Spring flowering shrubs bloom on "old wood" - on the previous season's growth - so the flowers actually developed on the plant late last summer. For maximum flower production next year, prune spring-flowering shrubs immediately after they bloom.
Summer and early-autumn flowering shrubs bloom on the current season's growth or "new wood". These plants should be pruned in late winter or just as growth starts in spring.