I can't find the thread where we talking about the diff between regular and dwarf Goats Beard, Aruncus. Several people mentioned that they wer having a hard time finding the dwarf variety. I was looking at a site (that, of course, doesn't sell them) but they gave it a different latin name: Aruncus aethusifolius instead of A. dioicus. And if you google it, there are a few different places that do sell it - the vendor list on DG has 6 places - Aruncus aethusifolius.

Hope this helps!