Butomus umbellatus is very easy to see and to identify. It is a tall plant (up to 1.5 meters) with showy white or pale pink flowers in a large umbel. There is no other species of that description in our emergent marsh flora. The leaves are triangular in cross-section, roughly similar to bur-reed (Sparganium eurycarpum) which is found in similar habitats.

Butomus umbellatus is not yet a widespread plant in Wisconsin, but it appears to have the potential to be a serious invasive species. It grows in marshes and can tolerate water as deep or deeper than that in which cattail is normally found (up to 2 meters), extending to the deepest range of our emergent marsh species, except possibly for hard-stem bulrush and wild rice. Once established in a marsh, populations increase and persist indefinitely. The good news is that it has spread very slowly from infested sites to other wetlands, and may be controlled if it is observed and destroyed within a few years of establishment.