Water hyacinth
Scientific: Pontederia crassipes (Previously Eichhornia crassipes [41])
Common: water-hyacinth, water hyacinth, common water-hyacinth, waterhyacinth, water-orchid
Family: Pontederiaceae (pickerel weed family)
Origin: Brazil [42]; South America [7, 11, 29, 34, 47].
Introduction History: First introduction to United States in Louisiana in 1884 at the Cotton Centennial Exposition, New Orleans as an ornamental aquatic garden plant [42]. First introduction to Florida was in 1890 [55]
General Description: An aggressive, free-floating aquatic perennial weed that rapidly reproduces, forming dense mats on the surface of freshwater habitats. Leaves are glossy and rounded, often borne on swollen, spongy leaf stalks that provide buoyancy. Showy lavender to purple flowers are produced on erect spikes above the foliage.
Habitat: Found in bodies of freshwater in tropical to subtropical latitudes globally [19, 25, 36]. Most wetland habitats including lakes, ponds, ditches, canals, slow moving water bodies, marshland, seasonal pools, floodplains, low-lying pastures [7, 29]. Intolerant of salt water [42].
Invaded Range: Frost-free tropics and subtropics globally. Southern United States (AL, AZ, CA, FL, GA, LA, MS, NC, SC, TX, VA (Horn, 2021)). Within Florida, vouchered in over 70% of counties [59] and probably more broadly distributed in freshwater wetland habitats [23].
Leaves: Sessile leaves form a basal rosette. Petiolate leaves floating or emersed. Petioles usually swollen, inflated, or thickened often resembling a pseudobulb. Leaf blade is ovate to round (≤ 6 inches wide) with a truncate apex. Leaves are bright green and glossy [2, 22, 27, 29, 34, 40, 42, 59].
Roots: Produces long, fibrous roots into the water column or into substrate in shallow areas. Roots are lighter when first produced, maturing to deep purple-black [34, 40, 42].
Flowers: Showy, spike inflorescence with 4-15 flowers, obovate spathes, glabrous. Erect and measuring up to 12 inches tall [21, 29, 34]. Flowers open in morning and wilt by night. Flowersblue to pale-purple with darker blotch in center and yellow spot within this [6, 29]. 2 inches wide [21, 29]. Flowering early spring to late fall [29].
Fruit: 3-locular capsule fruit [21].
Seeds: Seeds are small, forming in submersed, withered flowers [21] and have 11-14 wings [29]. Water and bird dispersed [6]. Sexual reproduction and self-fertilization is considered a trait which isdriven by insect pollination and has helped water-hyacinth persist in drought-prone areas [6, 8, 9, 10]. Seed germination may be associated with drawdowns or seasonal low water levels [34].
Other (Reproduction): Reproduces both sexually and asexually [25]. Asexually reproduction [7, 11] via stolons or rhizomes, forming dense, interconnected vegetative mats that rapidly cover waterbody surface. Fragmentation also promotes dispersion [6].
Dense mats can lower dissolved-oxygen and increase carbon dioxide concentrations within water bodies invaded by water-hyacinth negatively impacting ecosystem health (FWC, 2026; Mitchell, 1974; Ultsch & Anthony, 1973; Villamagna & Murphy, 2010)
Prolific organic matter deposition from annual biomass turnover of water-hyacinth can negatively impact nutrient cycling of water bodies (Barko & Smart, 1980; FWC, 2026; Gowanloch, 1944; Mitchell, 1974)
Water-hyacinth mats can impede access to water bodies, damage infrastructure, and increase flooding risk in rivers (FWC, 2026; Penfound & Earle, 1948; Webber, 1897).
This species, and other floating vegetation, can present human-health hazards by creating breeding habitats for mosquitos (Barber & Haynes, 1925)
Vigorously productive growth and dense mat development (Mitchell, 1979; Wolverton & McDonald, 1979) outcompetes native aquatic vegetation through competition for light (Carpenter & Lodge, 1986; Gowanloch, 1944; Penfound & Earle, 1948).
Water hyacinth should never be introduced into any body of water. It is prohibited by the state of Florida to cultivate, introduce, collect, and transport water hyacinth without a permit.
Very small infestations of water hyacinth may be controlled by handpulling. Water hyacinth thrives in nutrient-rich waters, so reducing nutrient concentrations in impacted waters, may decrease the vigorous growth of this plant.
Mechanical harvestors and chopping machines can be used to remove water hyacinth from the water and transport it to disposal on shore.
Three biological control insects have been imported, studied, and released to control water hyacinth. Together, these insects reduce the size and vigor of water hyacinth and reduce flower and seed production. Individually, however, they are not able to control water hyacinth. Click here to learn more.
Several registered aquatic herbicides provide temporary control of water hyacinth. See: Efficacy of Herbicide Active Ingredients Against Aquatic Weeds to learn more.
