These are growing in pots in a yard which sits on the pali (cliff ) overlooking the ocean. In fact, if you look closely at one of the photos, you can see a small barge in the water on the upper left side of the photo. These plants, locally referred to as tropical rhododendrons, do very well here on this island. As is often the case, most folks don't know which varieties they have, but that doesn't stop them from growing and enjoying them. Nor does it stop me from taking photos of them. aloha
There are many species and hybrids, should be plenty of scope for these in Hawaii. Yet, I have seen very few of them there, am therefore interested to see that you are growing some.
Here on the big island I didn't grow these. They belong to one of my customers. They have become very popular on the Big Island. I do believe they even have a local vireya club who along with the bamboo club planted many varieties at our Hilo zoo a few years back. I think I must see a new variety at least once a week. aloha, bob