Select Page

Flowering Rush

Butomus umbellatus
Home 9 Invaders 9 Aquatic Plants 9 Flowering Rush

What is Ontario Doing?

To prevent this unwanted invader from spreading in the province, Ontario has regulated flowering rush as restricted under the Invasive Species Act, 2015.  


Flowering rush is a perennial aquatic plant native to Eurasia and Africa that grows in lakes, riparian zones, wetlands, and marshes. It was first brought to North America from Europe in the 1800’s as an ornamental plant for ponds and water gardens.

Once it becomes established, it can out-compete native vegetation and create dense colonies that hinder recreational activities, such as boating, fishing, and swimming. It can spread between waterbodies via dispersal of seeds, rhizome fragments, and bulbils transported with boats, boat trailers, and other equipment. One risk is that any piece of the plant is capable of growing into a new plant.


Flowering rush was first recorded in 1897 along the St. Lawrence River in Quebec where it was used as an ornamental plant in ponds and outdoor water gardens. It likely escaped into the wild after being planted near or along shorelines and entered new areas as plant material was discarded into a waterway and/or carried off by flooding events. It is also suspected that ballast water from trans-Atlantic ships contributed to its introduction and spread.

In Ontario, it is found throughout the drainages of Lake Erie, Lake St. Clair, Lake Ontario, in the western St. Lawrence River, in central Ontario in the Severn River system, and northern Ontario in the Winnipeg River system.

For an up to date distribution of flowering rush in Ontario, visit

Impacts of Flowering Rush

  • Outcompetes native aquatic vegetation, reducing biodiversity.
  • Can hinder recreational activities, such as boating, fishing, and swimming.
  • Can impact habitat for wildlife, including native fish habitat and bird nesting and rearing sites.

How to Identify Flowering Rush

  • Numerous flowers on an erect, leafless flowering stalk over 1.5 m (4.9 ft) tall.
  • Flowers are stalked, emergent, and pink in colour with 3 sepals and 3 petals. 2 – 2.5 cm (0.8 –  1 in)wide.
  • Leaves are erect, floating, or submersed. 5 – 10 mm (0.2 – 0.4 in) wide, up to 2.7 m (8.9 ft) long.

What You Can Do

  • Learn how to identify flowering rush and how to prevent accidentally spreading this invasive species.
  • Avoid planting flowering rush in your water garden. Water gardeners should only use native or non-invasive plants and are encouraged to ask retailers for plants that are not invasive.
  • Dispose of invasive plants in the garbage. Do not put them in the compost or discard them in natural areas. Discarded flowers may produce seeds and seeds may sprout.
  • Avoid infested areas or reduce your speed when travelling by flowering rush infestations. Your propeller can break off fragments and spread the species to new areas.
  • Clean, Drain, Dry your vessel, trailer, and equipment after each use.
  • If you find flowering rush or another invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, visit EDDMapS, or search for the ‘Invasive Species in Ontario’ project on to report a sighting.


OFAH/OMNRF Invading Species Awareness Program. (2021). Flowering Rush. Retrieved from:
This factsheet may be reproduced for non-commercial purposes.

Reporting Invasive Species | Ontario's Invading Species Awareness Program

Think you have seen an invasive species?


Report it!


Invading Species Hotline



EDDMapS Logo

Available on the AppStore   Available on Google Play