Flowering Rush

Flowering Rush (Butomus umbellatus)

Report

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Photo credit: B. Brett

Management Category

ID Characteristics

General: Perennial, almond scented, aquatic plant. Flowering rush has two plant forms: emerged and fully submerged. Flowering rush is most distinguishable by its flowers, however it may not produce any.

Flowers: Pinkish-white flowers (three sepals with red anthers) form an umbrella-shaped cluster of 20-50 flowers at the end of each stem. Vegetative bulbils (small onion-like bulbs) grow on the flowers.

Stems: Flowering rush stems are green and can grow up to 1.5 m tall.

Leaves: Thin, straight, sword-shaped leaves that are dark green and have a triangular cross-section. When broken, the leaves exude a cob-web of white filaments. A fully submerged plant’s leaves are flexible and float at the surface. The leaves of an emerged plant are stiff and upright.

Fruits: Follicle fruits that contain many seeds. The seeds are straight and lined.

Roots: Shallow roots with rhizomes connecting plants. Rhizomes have vegetative bulbils on them.

Similar Species

Native

Common bulrush (Typha latifolia): Common bulrush, often called common cattail, is a native plant to British Columbia that closely resembles a Flowering Rush. However, the flowers of the two plants are very different.

Common bulrush is commonly identified by its large cylindrical seed pod, found on female plants. Plants are 0.9 – 2.7 m, and leaves are large, thin and tapered. Similar to flowering rush, common bulrush grows in wet environments including freshwater, marshes and shorelines.

Habitat and Origin

Flowering rush is native to Europe, Asia, and parts of Africa. It likely arrived in Canada and the United States in ship ballast waters or as an ornamental, probably in the early 1900s.

The fully submerged plants can be found in many aquatic ecosystems, including lakes, rivers, marshes, and streams. The emerged plants can be found on shorelines. Flowering rush often prefers shallow water but can survive in water up to 6 m deep.

How it Spreads

Flowering rush reproduces mainly vegetatively. The growing tips and fragments of the rhizomes and vegetative bulbils (small onion-like buds found on the flowers and the roots) can form new plants. Only some stands of flowering rush reproduce by seed.

Flowering rush is used as a garden ornamental and may be planted in aquatic gardens. Local dispersal can occur via water, human recreation, and the improper disposal of garden materials. Seeds, root fragments, and root bulbils can detach from the plants and disperse to new locations in the current. Flowering rush is considered a pioneer species, as it easily invades areas lacking plant diversity.

Impacts

Ecological:

Crowds out native vegetation.
Provides cover and nesting habitat for invasive fish species such as the Northern pike, walleye, smallmouth bass, and largemouth bass.

Health:

The presence of flowering rush has been linked to cases of Swimmer’s itch, as it provides ample habitat for the great pond snail, which hosts parasites that carry swimmer’s itch.

Economic:

Dense stands impede the use of shallow waters for boating and other recreational activities as well as irrigation systems.

Prevent the Spread

Flowering rush is found at only one site in Whistler, and three in all of British Columbia. The goal is to eradicate this species from the region and to prevent new introductions.

This is a high-priority species for the Province of BC, and it is included in the Early Detection and Rapid Response (EDRR) program.

Learn to identify flowering rush: use the images on this profile page to learn how to identify flowering rush.

What to do if you spot it: If you see flowering rush, please report it by visiting our reporting page.

DO:

Always clean, drain, and dry boats and equipment before leaving a water body (to avoid spreading floating seeds or plant parts).
Use caution when transporting your boat or other equipment from one province to another.
Regularly monitor properties for flowering rush and control new infestations.
Be PlantWise and choose alternative non-invasive species when selecting plants for a garden.
Minimize soil disturbances near flowering rush plants.
Ensure plants (particularly flowering heads or root fragments) are bagged or covered to prevent spread during transport to designated disposal sites (e.g. landfill).
Maintain riparian and aquatic environments in a healthy condition to ensure a productive natural plant community.

DO NOT:

Plant flowering rush in aquatic gardens, no matter how well-contained its enclosure may seem.
Purchase flowering rush at nurseries or garden stores.
Move water-crafts from water bodies where flowering rush has been reported to water bodies where flowering rush is not present without performing the Clean, Drain, Dry method.
Compost flowering rush!

Control

Flowering rush is very difficult to control.

Mechanical methods of control (cutting, digging, etc.) can be effective at decreasing abundance, however, these methods are problematic, as they can cause the spread of seeds, root fragments, and root bulblets.
Herbicide treatment is not possible at most sites, due to the plant’s aquatic habitat.
In any case, herbicide control is challenging and complex, and should not be attempted without seeking more information from the BC Ministry of Environment.
There are currently no biocontrol agents available for this species in BC.

Due to its limited distribution in BC, Flowering Rush is part of the Early Detection Rapid Response program in BC. SSISC is working with the BC Government to control the Whistler site.