- Butomus umbellatus is a perennial which spreads primarily from rhizomes. This aquatic plant invades along the margins of slow moving waterways. This plant can reach from 1-5 ft. (0.3-1.5 m) in height and can survive in water of up to 9.8 ft. (3 m) deep. It does not tolerate salt water.
- The leaves are linear, up to 3.2 ft. (1 m) long and triangular and fleshy in cross-section. The leaves may be erect or floating on the surface of the water.
- Flowering occurs in June to August, when umbels of small, 0.75-1 in. (1.9-2.5 cm) wide, pink to white flowers develop.
- The fruit is beaked which split at maturity to release the seeds. The seeds float which allows them to be easily dispersed by water.
- Ecological Threat
- This plant spreads mostly from rhizomes and occurs in wet areas with muddy soil, such as freshwater marshlands, lakes and streams. Butomus umbellatus can displace native riparian vegetation. It can form dense stands which are an obstacle to boat traffic. It is tolerant of a wide range of temperatures which gives it the potential to invade across much of the United States. Butomus umbellatus is native to Eurasia and was first found in Canada in the late 1800’s and in the United States in the early 1900’s.
Global Invasive Species Database. 2011. Invasive Species Specialist Group (ISSG) of the IUCN Species Survival Commission 
King County Department of Natural Resources and Parks Water and Land Resources Division 
Cooperative Invasive Species Management Area
Washington State Department of Agriculture 
Invasive Plant Atlas of New England
Oregon Department of Agriculture 
USDA NRCS PLANTS 
USDA ARS GRIN 
Images from Bugwood.org