Species At Risk

American Water-willow

(Justicia americana)


American Water-willow
American Water-willow occurrences map


The American Water-willow is an aquatic plant that grows 20 to 100 centimetres high. It has white or pale violet tube-shaped flowers marked with purple on the lower lip. The narrow leaves are eight to 16 centimetres long The fruit is a capsule that contains two to four beige or light brown seeds. The plant usually spreads by rhizomes and is capable of forming large colonies.

The flowers bloom in May or early summer, and bees are the main pollinators. The seeds mature from mid-July to the end of the summer when they are ejected from the plant and dispersed by water.


The range of the American Water-willow is limited to east central North America from Georgia and Texas north to New York, Michigan, southern Ontario and Quebec. In Ontario, it grows along the north shore of Lake Erie and in the Thousand Island region. There are only 10 locations in Canada where the plant is known to occur, and seven of these are in Ontario. Previously, 17 occurrences were known from Ontario and 11 from Quebec.


The American Water-willow grows along the shores and in the waters of streams, rivers, lakes, ditches and occasionally wetlands. It can grow on wet soil and in up to 1.2 metres of water, but appears to require periodic flooding and wave action to reduce competition from other aquatic plants. The underlying subsoil on which it grows is usually gravel, sand or organic matter.


The most significant threat to American Water-willow is habitat loss and degradation resulting from changes in water levels and water quality, potentially caused by dams and residential or industrial development. Individual plants may be harmed as a result of recreational activities such as boating. In some areas, invasive species such as the European Common Reed may be a threat to American Water-willow.


The American Water-willow receives protection under Ontario’s Endangered Species Act and the federal Species at Risk Act.

What You Can Do to Help the American Water-willow

  • The Ministry of Natural Resources tracks species at risk such as the American Water-willow. You can use a handy online form to report your sightings to the Natural Heritage Information Centre. Photographs with specific locations or mapping coordinates are always helpful. nhic.mnr.gov.on.ca
  • Report any illegal activity related to plants and wildlife to 1-877-TIPS-MNR (847-7667).
  • Private land owners have a very important role to play in species recovery. If you find American Water-willow on your property, you may be eligible for stewardship programs that support the protection and recovery of species at risk and their habitats.
  • Consult the Ministry of Natural Resources for information on provincial regulations and best management practices when working around wetlands and in forests. Call toll free 1-800-667-1940 or visit the Ministry website at www.mnr.gov.on.ca/en/ContactUs/2ColumnSubPage/STEL02_179002.html.
  • Pollinators, such as bees, are in steep decline across the globe and they play a key role in the survival of many of Ontario’s rare plants. For information on how you can help scientists monitor pollinator populations in Ontario visit: www.seeds.ca/proj/poll.
  • Invasive species seriously threaten many of Ontario’s species at risk. To learn what you can do to help reduce the threat of invasive species, visit: ontario.ca/invasivespecies ; www.invadingspecies.com ; www.ontarioinvasiveplants.ca ; and, www.invasivespecies.gc.ca .
  • Volunteer with your local nature club or provincial park to participate in surveys or stewardship work focused on species at risk.

Did you know?

American Water-willow (Latin name: Justicia americana) is named after James Justice who was an 18th century Scottish horticulturalist and botanist. “Americana” refers to the plant being native to the Americas.

Did you know?

The American Water-willow is well adapted to growing in areas that are disturbed by water level fluctuations. Because it spreads clonally by a thick underground rhizome, or horizontal stem, it can contribute to the stabilization of the banks of rivers and streams.

Did you know?

The American Water-willow is at the northern limit of its range in Canada, where it is relatively uncommon. Estimates of numbers of stems in Ontario, based on 2007 and 2008 counts, total approximately 100,000. In Quebec, totals for 2007 are estimated to be about 25.5 million.

Did you know?

The American Water-willow is the only member of the Acanthus family in Canada, a family consisting mostly of tropical species with centers of diversity in Indonesia, Malaysia, Africa, Brazil and Mesoamerica.

The Endangered Species Act

Contact your local ministry office

Often the best source of local information on species at risk is your nearest ministry office. Call with your questions or concerns.