Answer: Rhododendrons bloom in the spring so you'll want to wait until after they've finished blooming before you do any pruning. As soon as the flowers are spent you can prune by cutting each stem back by about one-third. Don't wait too long after blooming has finished to prune - rhododendrons use the summer months to develop the flower buds for next spring's display. If the foliage looks a little sickly, it's probably time to fertilize. Rhodies like acidic soil so a topdressing of peat moss beneath the plant will help acidify your soil. There are fertilizers formulated especially for rhododendrons that contain all the trace minerals they require for healthy growth. Be sure to apply in quantities as recommended on the package.
Rhododendron catawbiense Boursault produces many trusses of lavender purple flowers which may completely hide the foliage. It blooms in mid-spring, has a dense growth habit and will reach 5' in height and width in 10 years. It is cold hardy to -20?F. It's a tough plant that takes both heat and exposure to full sun.
Best wishes with your rhodie!
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