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Part of Invasive aquatic plants

Flowering rush

Flowering rush (Butomus umbellatus) can reduce irrigation water availability and impede aquatic activities like boating or swimming.

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Invasive aquatic plants

Place of origin

Originally from Eurasia, flowering rush (Butomus umbellatus) it was introduced as an ornamental garden plant in the 1890s. This invasive aquatic plant is now found across Canada and the United States.

Habitat

Can grow as an emergent plant along shorelines or partially submerged in lakes and rivers up to 4 m in depth.

Identification

Flowering rush infestation

Flowering rush flowers in front of infestation at Lake Isle, Alberta

Photo of Flowering rush flower

Flowering Rush flower up close. 3 petals, 3 sepals arranged in clusters on a flower stalk.

 

Photo of Flowering rush infestation

Flowering rush, once introduced will quickly dominate shorelines, as emergent and submerged plants.

 

Photo of Flowering rush plants

Overall view of flowering rush plants. Note shallow root system and red leaves end at water line.

 

Photo of a Close up of flowering rush stem cross section.

Flowering rush triangular stem cross sections. Stems for this plant have a sponge-like consistency and are easily compressed.

 

Photo of close-up of flowering rush roots.

Flowering rush roots. Stacked rhizomes are shown as well as bubils; both are capable of breaking off to start new plants elsewhere.

  • A perennial, surviving winters and droughts.
  • Cross section of leaves is triangular, while the flowering stem is round.
  • Easiest to identify when flowering in summer months. Each umbrella-shaped cluster has whitish pink petals. Flowers are only produced in very shallow water or on dry sites.
  • Looks similar to cattails (Typha latifolia), rushes (Juncus spp.) and bur-reeds (Sparganium spp.).

Reproduction

  • Can reproduce by root system fragments or rhizome buds called bulbils.
  • Seed production is yet to be observed in North American populations.

Issues

  • Dense stands in irrigation ditches can reduce water availability, and in lakes can interfere with boat propellers and swimming.

Current management in Alberta

The Alberta government has partnered with several organizations to study flowering rush eradication methods on Lake Isle and Chestermere Lake. The following methods have all been tested in Alberta:

  • Bottom barriers
  • Diver assisted suction harvesting
  • Hand digging
  • Herbicide treatments
  • Mechanical harvesting

Hand digging and herbicide treatments are the most feasible treatments, but they have their limitations with effort and approvals.

Herbicide applications to decrease the population and density of flowering rush were also used in Buffalo Creek near Innisfail.

Resources

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