Answer: You can prune only a few inches off of single branches or all over the plant but you don't need to prune back by one third unless the rhodies are completely overgrown. Rhodies spend the summer months developing new stems and flower buds for the next year's floral display. Cutting them back by just just a few inches each year will help keep them full and thick, and with plenty of flowers. Hope this clarifies things for you.
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