This isn't really an answer to your question. Just wanted to say that I had the same problem this year. I did have a few flowers but they were very sparse. For a change I had tried a different type - can't remember the name - but they were all supposed to be the same kind of salmon pink. Mine were in a very large tub with a wigwam - looked after very carefully and like you, lots of greenery but very few flowers.

I think I'll go back to the usual type next year!

Was it cold at bud formation time?

What did you feed them with?

Was it an early flowering or summer flowering type, and when was it planted?