Rexes are highly variable from juvenile to adults. Fireworks is an excellent example of this - the juvenile looks nothing like the mature plant it will become.

Dale Sena is an upright jointed rhizome (from my layman's perspective). The leaves look like rex (maybe it is) but the plant can get a lot taller than a rex.

Yes, thanks for reminding me that I need to look closely at "new varieties" I buy and bring home, only to find after a few months that they mature into something I already had.

Since you bring up "upright joined rhizome," is there a source that we can refer to that actually defines the various types of begonias? I couldn't find anything at Brad's or at ABS either. Even wikipedia had some obscure "descended from and Indian" something-or-other.

There is no one source that defines all the various begonias (seems to be a blurry line out there). You will see a class of UJR on the ABSASTRO site of cultivars.

Brad's Defs

Forgot to add them to my list of references. Yes, I refer to ABSASTRO quite often and have found the names from that site to much of what I buy. Thanks for your input!