This is interesting indeed!
But I don't understand how it grows.
Does it shoot runners under the gravel and a new little "palm" pops up on the other end?
Also the emersed form seems very nice, while the submersed maybe not so nice? It looks like a definite emersed grower. How nice will it look submersed? The pictures I find look like recent transplants to sumbersed.
Both pictures taken from here: http://www.flickr.com/photos/danielc...in/photostream