Thanks for the encouragement, Char! If I come across TFF again I will give it another try. I know these things can happen for no obvious reason, the first 'Cherry Cheeks' I got dwindled away to nothing - I tried it again and the second plant has been excellent and I've had it for years, so it's not always the cultivar per se. If I'd based my opinion on the first one I'd have thought it was a weak plant, but the second is far from that.
I do have 'Bee's Bettie Sue', a parent of 'Michael's Sword' and 'Bee's Bob Baker', and it has done well here so far - it has had pretty much all plain flowers though but lots of them. It's planted in the same bed that TFF was and acquired at the same time so I don't know for sure what TFF's problem was.
