Native Range

South America

Appearance

Waterhyacinth is an upright, herbaceous, and free-floating aquatic perennial that grows between 2 in (5 cm) and 3S ft (1 m) tall. Plants grow a dense mat of feathered, dark-colored roots as well as lightercolored stolons that produce daughter plants. Each plant consists of a cluster of basal leaves arranged spirally. In uncrowded situations, leaf stalks are spreading and have pronounced, buoyant swelling. In dense stands, plants are taller and leaf stalks grow more erect with little or no swelling. Leaf blades are rounded or kidney-shaped, waxy, leathery, and up to 6 in (15 cm) across. Flowers occur in a single spiked cluster. Each flower has six purple-blue petals, and the top petal has a bright yellow spot surrounded by darker purple. Fruits are capsules containing up to 450 small, ribbed seeds.

Impact

Waterhyacinth displaces native species, impedes water flow and water navigation, and damages fishing, hunting, boating, swimming, and other recreational sectors. Decaying plant material can decrease oxygen levels which is detrimental to fish and other organisms.

Reference

Smith, M.C., A.B.C. Goode, and N.E. Harms. 2022. Waterhyacinth (Pontederia crassipes): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-16-WATERHYACINTH-P. https://bugwoodcloud.org/resource/files/25357.pdf

Selected Images

Maps

Invasive Listing Sources

• Alabama Invasive Plant Council
• Alabama Noxious Weeds - Class C Noxious Weed
• Alachua County Cogongrass Initiative
• Apalachicola Invasive Working Group
• Arizona Noxious Weeds
• California Invasive Plant Council
• Connecticut Invasive Plant Working Group
• Florida Invasive Plant Council - Plant List - Category I
• Florida Noxious Weeds
• Georgia Exotic Pest Plant Council - Category 1
• Idaho Noxious Weeds
• Invasive Plant Species of West Virginia
• Invasive Species of Concern in Georgia
• John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
• Kentucky Exotic Pest Plant Council
• Maryland Aquatic Nuisance Species Plan
• Maryland Department of Natural Resources Policy: Restriction on Planting Exotic Invasive Plants
• Maryland Invasive Species Council - Invasive Species of Concern in Maryland
• Michigan’s Invasive Species Watch List
• Mid-Atlantic Field Guide to Aquatic Invasive Species
• Minnesota DNR invasive species list
• National Park Service, Mid-Atlantic Exotic Plant Management Team Invasive Plant List
• National Park Service, National Capital Region Exotic Plant Management Team Invasive Plant List
• Native Plant Society of Oregon, 2008
• New Hampshire Invasive Plant Species Watch List
• New Hampshire Invasive Species Committee. 2005. Guide to Invasive Upland Plant Species in New Hampshire. New Hampshire Department of Agriculture,  Markets and Food Plant Industry Division and New Hampshire Invasive Species Committee.
• New Jersey Invasive Species Strike Team 2017 Invasive Species List
• Nonnative Invasive Species in Southern Forest and Grassland Ecosystems
• Ontario’s Invading Species Awareness Program Tracked Species List
• Rhode Island Natural History Survey
• South Carolina Illegal Aquatic Plants
• South Carolina Invasive Pest Council
• South Carolina Plant Pest List
• Texas Noxious Weeds
• Virginia Invasive Plant Species List
• WeedUS - Database of Plants Invading Natural Areas in the United States
• Wisconsin Noxious Weeds
• Wisconsin's Invasive species rule – NR 40