Flowering rush (Butomus umbellatus)


Description:

Appearance: Perennial aquatic herbaceous plant. It grows 1-4' high on an erect stem along shores in shallow water. In deeper water it grows submerged without producing flowers. Flowering rush is very difficult to identify when not in flower. It closely resembles many native shoreland plants, such as the common bulrush.

Leaves: Leaves are sword-shaped, triangular in cross section.

Flowers: Pink flowers are arranged in umbels (umbrella-shaped).

Seeds: Populations in the eastern U.S. produce seeds. Only one Minnesota population (Forest Lake) produces viable seeds.

Roots: Reproduces by vegetative spread from its rootstock in form of bulb-lets. Both seeds and bulb-lets are dispersed by water current.

DNR aquatic plant regulations for permits to remove flowering rush.

Map of flowering rush infestation in Minnesota
Flowering rush infestation in Minnesota.

Ecological Threat:

  • Flowering rush is actively expanding. It has spread from a limited area around the Great Lakes and the St. Lawrence river to sporadically appear in the northern U.S. and southern Canada.
  • It competes with native shoreland vegetation.
  • It is a Eurasian plant that is sold commercially for use in garden pools. It is now illegal to buy, sell or possess the plant.
  • There is documentation from a site in Idaho, between 1956 and 1973, where flowering rush appeared to be out-competing willows and cattails.
  • Flowering rush is on the DNR Prohibited invasive species list in Minnesota.

 

Control Methods:

A permit is required to work in public waters

Mechanical
Cut below the water surface several times per summer, remove cut parts from water. This will help control spreading.

Hand dig isolated plants with care, root fragments can spread and sprout
 

Chemical
Application of imazapyr (Habitat)

Preliminary testing indicates that a mid-summer application during calm wind conditions may be most effective


Native Substitutes:

Additional Resources