As a comment about Giant Japanese Butterbur (Petasites japonicus subsp. giganteus 'Nishiki-buki')
While the blooms aren't precisely showy, I wouldn't describe them as inconspicuous, at least here in my zone. This year and last the blooms have been some of the first green to emerge, and they definitely attract attention. The leaves are obviously the main attraction, so I'm hoping my clump has more big leaves this year. They should play nicely with a few Elephant Ears. I haven't noticed any rampant spreading yet, but the plant is definitely vigorous. I'm growing it in part sun/shade with plenty of water.
The petioles were a bit tough when broiled, but I'll try them again this year with, hopefully, newer and larger ones.
Update: 25April2015. Very vigorous!!! In two years I have leaves emerging two feet away on all sides. I'm going to have to move the clump to a new location where it can spread as much as it wants, if it can compete with tree and shrub roots.