Answer: Rhododendrons develop leaf and flower buds during the summer months so pruning in September will likely remove next year's flower display. If possible, wait until after flowering has finished next spring and then prune your rhodies. Prune by late June and you should still have plenty of flowers for the next year.
The general rule of thumb is to prune shrubs immediately after they have finished flowering. If you have evergreens that do not flower, early spring is the best time to prune them.
Hope this answers your question!
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