Butomus umbellatus • Class A

An emergent, aquatic perennial, Flowering Rush is the sole species of the Butomaceae plant family. 

Plants grow from 1 to 5 feet tall, on cylindrical stalks topped by umbrella shaped clusters of 20 to 50 light pink flowers.  Flowers have 3 large petals, 3 sepals, 9 stamens and pistils.

Blooms from June to August.

Its sword-like leaves grow from stout rhizomes, and may be submerged, floating or emerge from water.

Flowering Rush is an invasive aquatic plant that competes with native wetland and shoreline species and can crowd out desirable vegetation.   It is an aggressive colonizer, and difficult to control.  

Flowering Rush is found in freshwater habitats. It roots in the mud along lake shores, slow moving rivers, irrigation ditches, and wetlands. It typically grows in shallow waters, but can survive in water up to 9 feet deep.

Seeds and plant fragments are dispersed primarily by wind and water, but may also be spread by waterfowl, wildlife, or boating equipment.

In addition to rhizomes and rhizome fragments, it reproduces by forming vegetative bulbils (little pea-sized bulb like sprouts) on the rhizomes and at the base of the flower stalk.  Some, but not all, plants reproduce by seeds. 

• Flowering Rush is difficult to control and research continues on control options.

• Hand digging, or suction dredging by hand before seed set, may be a control option for small isolated infestations or individual plants.   Be careful to remove all root fragments, disturbing the soil around the plant roots as little as possible, as this will spread the rhizome bulbils.  Repeated digging will be required. Remove and dispose of all plant and rhizome fragments away from water.

• Since Flowering Rush is found in wetland areas, the use of an herbicide formulated for aquatic settings is required. Please note that aquatic herbicides are restricted for use in Washington State to licensed applicators only. 

For more information on this noxious weed  Download our Flyer or visit Washington State Noxious Weed Control Board Here. Photos by Beki Shoemaker, Pierce County Noxious Weed Control Board.