Some rhodendrons have a tendancy to Fall bloom. Most notably is David Leaches "Last Hurrah", a deliberate attempt to market a Fall bloomer. Almost any Rhododendron will occassionally throw off a few flowers in the Fall if the weather changes to a wet and warm Fall.
R. oldhamii and its hybrids (Encore, etc) rebloom. There are a few others that also do. The Evergreen Azalea 'Chinzan' and R. 'Everlasting' bloom over a long period rather than once. Evelasting had been sold as R. nosuchianum, undr the belief that it was half Kalmia, and no such thing could happen.
Hi,, I have (one) of several Rhododendrums that just started blooming. I will try to take a pic tomorrow. It is about 9 years old. the others of the same variety are not blooming. I am slowly putting a sprinkler system in and it is one that got a "little" more water than the others during this awful drought we are having. So I think water may be the key.. Just a guess,,,