You can trim flowering shrubs lightly anytime of the year especially if you are just removing dead, broken or diseased branches. Avoid pruning plants in late fall because it stimulates new growth which is easily damaged by freezing temperatures. For most shrubs, late winter or early spring is a good time for heavy pruning, but be sure to check the recommendations for your specific shrub. Some flowering shrubs like Hydrangeas can bloom on old wood so pruning in winter or spring can remove flower buds.
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