Water hyacinth is a free-floating aquatic plant in the Pickerel-Weed family (Pontederiaceae) imported into North America in 1884 for an exposition in New Orleans. New introductions are probably the result of improper disposal of pond plants or when ponds adjacent to local water bodies overflow with rains. Water hyacinth is readily available for purchase as an ornamental plant of ponds and outdoor water gardens in Ontario, where it is not a regulated species. Naturalized populations have caused widespread ecological, economic and recreational impacts.


Water hyacinth is native to the upper Amazon River basin in South America but its distribution is now widespread around tropical and subtropical regions of the world. Populations are generally found in warmer southern United States, located around the Gulf of Mexico and California, but have also been reported in many northern states and in isolated locations in Ontario (Essex County). It is assumed to not overwinter or naturalize in these locations because of the cold climate.

Impacts of Water Hyacinth

Where conditions are right, water hyacinth grows and spreads rapidly over very large areas in a short time period, forming continuous, dense floating mats up to 2 metres thick. These characteristics may lead to the following impacts:

  • Out competes and/or displaces native species for space, light, and nutrients.
  • Reduced oxygen levels under water hyacinth mats can alter the composition of invertebrate and fish communities. This occurs because thick mats of water hyacinth block the air-water interface.
  • Slow down water flow, blocks irrigation canals, delays hydroelectric and water treatment plants.
  • Interferes with recreational activities such as boating, swimming and fishing.
  • Threatens biodiversity and human health by creating prime habitat for disease vectors, such as mosquitoes.

How to Identify Water Hyacinth

  • Leaves are floating or emergent and form a rosette.
  • Leaf blades are bright green, thick and glossy, egg-shaped to round, on an inflated leafstalk that is filled with spongy tissue.
  • Roots are fibrous, dark purple/black and hang beneath the rosette.
  • Flowers are loosely clustered with 4-15 flowers on a spike above the rosette, six blue-violet petals with one petal being deeper violet with a yellow spot.
  • Fruit is a capsule with many seeds.
  • Stolons extend outward from the parent plant to produce new plants.

What You Can Do

  • Learn how to identify water hyacinth and how to prevent accidentally spreading this plant with your watercraft.
  • Do not plant water hyacinth in your pond or water garden. Water gardeners should only use native or non-invasive plants and are encouraged to ask garden centers for plants that are not invasive.
  • Never release unwanted plants into any natural waterbody. Return or donate unwanted plants to a garden center, a school or a friend, or dispose of them in the garbage.
  • Avoid infested areas or reduce your speed when travelling by water hyacinth infestations; boat wake can separate offsets and allow them to spread.
  • Always inspect your boat and boating equipment, and remove any plants, animals and mud that are visible before leaving the water body.
  • Rinse all recreational equipment with high pressure (>250 psi), hot water (50°C / 122°F) OR let it dry in the sun for at least 5 days.
  • If you find water hyacinth or other invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, or visit EDDMapS Ontario to report a sighting.


OFAH/OMNRF Invading Species Awareness Program. (2012). Water Hyacinth. Retrieved from:
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Header photo by Wendy VanDyk Evans,