Native Range

Europe and Asia

Appearance

Flowering rush is an aquatic perennial with fleshy, rhizomatous roots. In shallow water or along shorelines, flowering rush is emergent and produces showy pink flowers, each up to 1 in (2½ cm) across, in umbels on round leafless stems that grow up to 3.2 ft (1 m) tall. Plants can also grow completely submerged in deeper water where they do not flower. Emergent leaves are somewhat rigid, twisted, and grow upright up to 3 ft (90 cm). Submerged leaves are more flattened, limp, and grow up to 10 ft (3 m) long. Flowering plants produce 6-chambered fruits. When viable seeds are produced, they are small, brown, and cylindrical.

Impact

Flowering rush creates dense stands that impede water flow and damage fishing, hunting, boating, and other recreational activities. It acts as an ecosystem engineer, creating floating mats and encouraging sedimentation under dense stands. It invades previously non-vegetated areas, displaces native plant species, increases water temperature, alters habitat structure and nutrient cycling, and may provide substrate for invasive mussels as well as aquatic snails serving as the intermediate host for the swimmer’s itch parasite. In some locations, such as the Columbia Basin, there is concern that flowering rush can provide increased habitat for predatory non-native fish species, including northern pike and smallmouth bass which feed on native trout and salmonid species.

Reference

Andreas, J.E., J.K. Parsons, J.D. Madsen, and R. Bourchier. 2025. Flowering Rush (Butomus umbellatus): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2025-6-FLOWERING RUSH-P. https://bugwoodcloud.org/resource/files/33593.pdf

Resources

• Species Profiles - University of Minnesota
• Global Invasive Species Database - Invasive Species Specialist Group

Selected Images

Maps

Invasive Listing Sources

• Alberta Fisheries Act
• Alberta Weed Control Act
• Colorado Noxious Weeds
• Connecticut Invasive Plant List
• Connecticut Invasive Plant Working Group
• Connecticut Noxious Weeds
• Hoffman, R. & K. Kearns, Eds. 1997. Wisconsin manual of control recommendations for ecologically invasive plants. Wisconsin Dept. Natural Resources, Bureau of Endangered Resources. Madison, Wisconsin. 102pp.
• Idaho Noxious Weeds
• Indiana Invasive Species Council - Invasive Plant List
• Indiana Pest Species
• Indiana Prohibited Plant Species
• Maine Invasive Plants
• Maryland Aquatic Nuisance Species Plan
• Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
• Massachusetts Invasive Plants Advisory Group List
• Massachusetts Noxious Weeds
• Massachusetts Prohibited Plant List
• Michigan’s Prohibited and Restricted Species
• Mid-Atlantic Field Guide to Aquatic Invasive Species
• Minnesota DNR invasive species list
• Montana Noxious Weeds
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• Nevada EDRR
• Nevada Noxious Weeds
• New Hampshire Prohibited Aquatic Species
• Ohio Invasive Species Council
• Ontario’s Invading Species Awareness Program Tracked Species List
• Oregon Noxious Weeds
• Pennsylvania Department of Conservation and Natural Resources Invasive Plants
• Pennsylvania's Field Guide to Aquatic Invasive Species
• To be proposed for MISC
• Vermont Noxious Weeds
• Washington Noxious Weeds
• WeedUS - Database of Plants Invading Natural Areas in the United States
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40

References