Rhododendron – How/When Do I Prune?
Q: How and when I can prune back a large rhododendron?
A: In late summer, it’s best to split the job into two parts. Remove about 25% of the plant this winter but leave some of the shorter limbs that have flower buds on them so you can enjoy blooms next year. After the rhododendron blossoms next spring you can remove another 25%. That should bring the size more to your liking.