Background

Water hyacinth is a free-floating, aquatic plant in the pickerel-weed family (Pontederiaceae spp.) 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 waterbodies become flooded. Water hyacinth is readily available ornamental plant for purchase that is typically put in ponds and outdoor water gardens in Ontario, where it is not a regulated species.

Range

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 have been 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 thought to be an annual in cooler climate environments, such as Ontario.

For an up to date distribution map of water hyacinth in Ontario, visit EDDMapS.org/Ontario/distribution.

Impacts of Water Hyacinth

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

  • Out competes and/or displaces native species for space, light, and nutrients.
  • Reduces oxygen levels under water hyacinth mats, which 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, and 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, and 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 to 15 flowers on a spike above the rosette. Flowers have 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.
  • Clean, Drain, Dry your boat, trailer, and boating equipment. Remove any plants, animals, and/or mud that is visible before leaving the waterbody.
  • If you find water hyacinth or another invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711, visit EDDMapS Ontario, or search for the ‘Invasive Species in Ontario’ project on iNaturalist.org to report a sighting.

Gallery


OFAH/OMNRF Invading Species Awareness Program. (2012). Water Hyacinth. Retrieved from: www.invadingspecies.com.
This factsheet may be reproduced for non-commercial purposes.

Header photo by Wendy VanDyk Evans, Bugwood.org