Flowering rush

Quick facts

Flowering rush is a prohibited invasive species. It is illegal to possess, import, purchase, transport, or introduce these species (including hybrids or cultivars) except under a permit or statutory exemption. Transport directly to the Minnesota Department of Natural Resources in a sealed container for identification or reporting purposes is permitted.

Flowering rush can produce dense monotypic stands.
May displace native species and interfere with boat traffic.
Flowering rush should be reported.

See the Minnesota Department of Natural Resources recommendations for reporting invasive species.

pink flowering rush in a small body of water

How to identify flowering rush

Flowering rush (Butomus umbellatus) is a perennial aquatic herbaceous plant that grows up to six feet tall along shores in shallow water.
Can grow submerged in water up to ten feet without producing flowers.
When not in flower, it looks like common native shoreland plants and may be difficult to identify.

Stem

Triangular in cross-section, may be more rounded toward the base.

close up of pink flowering rush cluster of buds — Flowering rush

Leaves

Sword-shaped, triangular in cross-section, often twist near top.

Flowers

Roots of flowering rush — Flowering rush bulbils

Pink flowers are arranged in umbrella-shaped clusters (umbels).
Blooms from late June to August.

Seeds

Populations in the eastern U.S. produce seeds.
Only one Minnesota population (Forest Lake) is known to produce viable seeds.

Roots

Reproduces by vegetative spread from its rootstock in the form of bulbils.
Both seeds and bulbils are dispersed by water current.

Angela Gupta, Extension educator; Amy Rager, Extension educator; Megan M. Weber, Extension educator

Reviewed in 2019