The main problem with rhododendrons is that the hybrids that you
purchase in most nurseries are propagated by grafting on to ponticum.
The result is that the ponticum takes over unless they are carefully
watched. I would always when buying rhododendron hybrids to ask the
seller whether they are grafted or propagated on their own roots. My
advice is to REJECT GRAFTED HYBRIDS.

Regards
Don