Butomus umbellatus

Keys to Identification

• The leaves are triangular
• Flowers are three-petaled with three same colored sepals below

Family

Butomaceae – Flowering rush family

USDA Code

BUUM

Legal Status

Colorado Noxious Weed List A

Identification

Lifecycle

Perennial aquatic

Growth form

Resembles rushes.  Grows erect in semi-submerged areas and leaves float on the surface of deeper water.

Flower

Flowers are pink to white, 1 inch wide, 3 petals with 3 petal-like sepals, 20-50 in umbrella-shaped clusters
Flowers July-September

Seeds/Fruit

Fruit deep brown, about ½ inch long, filled with tiny seeds. At maturity the fruit splits to release the seed.  Most seed is not viable

Leaves

Emergent leaves basal, sword-like, to 3 ½  feet long and ½ inch wide, triangular, curved at the end.  Submersed leaves limp

Stems

Plants are up to 5 feet tall
Stems erect and triangular

Roots

Thick creeping rhizomes have bulblets that can easily break off and form new plants

Impacts

Ecological

Displaces native plants.  May form thick monocultures and may interfere with access to water

Human

May interfere with recreational access to water bodies

Habitat and Distribution

General requirements

An escaped ornamental.  Found in lakes, ponds, and slow-moving water

Distribution

A few plants were found in Mesa County in 2018

Historical

Native to Europe and Asia

Biology/Ecology

Mode of reproduction

Reproduces by bulblets, rhizomes and vegetatively

Other

Not a true rush, it is the only genus in the Butomaceae family

Muskrats use pieces of the plant to build their homes and may contribute to the spread

Photo by: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org