(Question)
I have a very robust 5 foot wide rhododendron that is now about 20 years old, started from a small nursery plant. My question is, can I safely take a section of it to replant elsewhere in the garden without harming the plant?
(Answer)
It is not possible to successfully split a rhododendron, but you can propagate them to add to your collection!
The best methods for home gardeners are layering and cuttings, both of which techniques are very well described in this publication of the American Rhododendron Society. Virginia Tech has some additional information on cuttings.