Shoreline and shallow-water plant
Flowering Rush
Butomus umbellatus
These illustrations are AI-generated, not photographs, and are not to scale. They show what to look for; they are not a substitute for an expert identification.
How to identify it
Size: Grows along shores and in shallow water. It can also grow completely underwater, where it does not flower.
- Long, narrow leaves that are triangular when you cut across them, often twisting near the tip.
- In summer, a rounded, umbrella-shaped cluster of pink-to-white flowers on a tall stalk.
- Each flower has three broad petals and three smaller sepals, with darker veins and red centers.
Don’t confuse it with
Without flowers it can pass for native bulrushes or bur-reeds. Flowering rush's leaves are triangular where you cut across them and often twist near the tip. Bulrushes are mostly bare stems with their leaves reduced to sheaths at the base, and some native bulrushes have three-sided stems of their own, so shape alone does not settle it. If you are not sure, report it.
Where it came from
Native to Europe and Asia.
Brought to North America as a garden plant and first recorded along the St. Lawrence River in the late 1800s. It spreads by root pieces and small bulb-like buds that break off and float away.
Earliest dated Michigan record: 1905, the Detroit River. This is the oldest dated record in the USGS non-native species database, not necessarily when it first arrived.
Why it matters
It forms dense stands along shores and in shallow water that crowd out native plants and can get in the way of swimming and boating.
Michigan law
Restricted under Part 413 of Michigan's Natural Resources and Environmental Protection Act. It is illegal to possess, introduce, import, sell or offer to sell it as a live organism, except in the limited cases the law allows. The state uses “restricted” for species already established in Michigan. The state’s page on this species.
If you find it
- Don’t move it. Michigan law requires boaters to remove all aquatic plants from boats, equipment and trailers before launching. Before trailering, you must pull all drain plugs, drain live wells and bilges, and make sure the boat and trailer are free of aquatic plants and animals. What the law requires
- Never release bait. Releasing baitfish into Michigan waters is illegal. Put unused bait in the trash, never in the water.
- Report it. Take a photo, note where you saw it, and report it to the Midwest Invasive Species Information Network (MISIN) or through Michigan’s invasive species program. Experts there can confirm what you found.
- Ask before removing or treating. Treating a lake with herbicides or other chemicals needs a state permit, and some removal work does too. Start with the state’s Aquatic Nuisance Control program before taking action.
Michigan lakes where it has been recorded
23 Michigan lakes on this site have a record of this species.
Alger
Calhoun
Genesee
Jackson
Livingston
Macomb
Oakland
Cass Lake, Cranbrook Lake, Kent Lake, Lakeville Lake, Lower Pettibone Lake, Maceday Lake, Orchard Lake, Pontiac Lake, Proud Lake, White Lake
Ogemaw
Van Buren
Washtenaw
A lake that is not listed may still have it. Records exist only where someone found the species and reported it, so “not recorded” does not mean “not present.”
Lake records: Midwest Glacial Lakes Partnership Conservation Planner; underlying records from the USGS Nonindigenous Aquatic Species database.
Sources
- Michigan Invasive Species Program: Flowering rush
- University of Nevada Extension: Flowering rush
- Michigan Compiled Laws, section 324.41302 (prohibited and restricted species)
Earliest dated record: USGS Nonindigenous Aquatic Species database.