Species Description: Water hyacinth, Eichhornia crassipes is a floating, invasive non-native plant commonly encountered as dense mats in Florida freshwater habitats.
Several features make E. crassipes easy to recognize, including rosettes of rounded and leathery, waxy, glossy green leaves attached to thick, spongy (often bulbous or inflated for floatation) petioles (stalks), dark feathery roots that typically hang suspended in the water below the floating plant, and attractive lavender flowers when the plants are in bloom. The inflorescence is a distinct aerial spike growing to 30 cm, the flowers have six stamens, and the fruit is a 3-chambered seed capsule (Langeland and Burks 1998, UF/IFAS 2001).
Potentially Misidentified Species: In Florida, Eichhornia crassipes may be confused with the floating form of a somewhat similar appearing native aquatic plant, frog's bit (Limnobium spongia). The presence of small, white flowers and petioles that are not bulbous or inflated aid in distinguishing the native plant from water hyacinth (Langeland and Burks 1998).
Regional Occurrence: Eichhornia crassipes can be found in all types of Florida freshwater habitats. The species is native to the Amazon Basin of Brazil but has been introduced to tropical and subtropical regions around the world (Langeland and Burks 1998). Holm et al. (1977) noted that at the time of publication 56 countries including the United States had reported it as a noxious weed.
Within the U.S., E. crassipes occurs throughout the southeast north to Virginia and west to Texas, as well as in California and Hawaii. Seasonal escapes from cultivation are reported from New York, Kentucky, Tennessee and Missouri, but populations apparently do not survive through winter. The plant previously occurred in Arizona, Arkansas, and Washington State but is now considered eradicated in these locations (Ramey 2001).
E. crassipes occurs in all but a handful of counties in the Florida peninsula and about half the counties in the panhandle and north Florida (FLEPPC EDDMaps).
IRL Distribution: Eichhornia crassipes is a freashwater species that is widespread in all six counties within the IRL watershed.
Age, Size, Lifespan: Aerial portions of Eichhornia crassipes generally grow to 0.5 m in height, although individuals in some Asian populations may reach nearly 1 m (Gopal 1987).
Abundance: Water hyacinth mats are capable of attaining incredibly high plant density and biomass. A single hectare of dense E. crassipes mat can contain more than 360 metric tons of plant biomass. Exhaustive management efforts in Florida over the last 20 years have considerably reduced the amount of aquatic habitat choked by this invader (UF/IFAS 2001).
Reproduction: Water hyacinth is capable of sexual and asexual reproduction and both modes are important to the species' success as a pernicious aquatic invader. In mild climates, plants can flower year-round, and from early spring to late fall elsewhere. They can produce an abundance of seeds (Flora of North America 2003, Langeland and Burks 1998). A study by Barrett (1980b) confirmed that tropical E. crassipes populations produced twice as many seeds as did temperate populations and attributed the difference to higher rates of pollinating insect visitation in the tropics. Seed germination tends to occur when water levels are down and the seedlings can grow in saturated soils.
Vegetative reproduction occurs via the breaking off of rosettes of clonal individuals. The stolons (horizontal shoots capable of forming new shoots and adventitious roots from nodes) are easily broken by wind or wave action and floating clonal plants and mats are readily transported via wind or water movement (Barrett 1980a, Langeland and Burks 1998).
Embryology: E. crassipes produces a thin walled, capsule-like fruit that is protected within structures that form from the perianth, the outer whorls of the flowers. Each capsule can hold as many as four hundred-fifty 4-mm long x 1-mm thick seeds (Gopal 1987). Germination typically occurs in wet soil.
Temperature: Although Eichhornia crassipes is excluded from cold climates due to temperature limitations, it does exhibit a degree of freeze tolerance. Aerial portions of the plant killed back by moderate freeze events can quickly regrow from submerged stem tips protected from freezing by water (Langeland and Burks 1998).
Salinity: Holm et al. (1977) indicate that water hyacinth is intolerant of brackish conditions. Experimental studies by de Casabianca and Laugier (1995) demonstrated an inverse relationship between salinity and Eichhornia crassipes plant yield; no plant production and cankerous plants resulted at salinities above 6 ppt and irreversible physiological damage occurred above 8 ppt. Water hyacinth is capable of growing in low salinity coastal lagoon habitats, e.g., in West Africa during the rainy season (ISSG).
Trophic Mode: Autotrophic (photosynthetic).
Associated Species: Small forage fish utilize the floating mats and suspended root masses as a refuge, although anthocyanins and other soluble plant pigments in the roots may protect them from herbivores (Gopal 1987).
Invasion History: The U.S. invasion history of water hyacinth is well documented. The Brazil native was first introduced to the U.S. as an ornamental aquatic plant at a New Orleans, LA exposition in 1884. Eichhornia crassipes escaped from cultivation to arrive in Florida by 1890, and over the ensuing 60 years, dense mats of this highly invasive plant had taken over more than 50,000 ha of Florida freshwater habitat (Gopal and Sharma 1981, Schmitz et al. 1993).
The amount of Florida aquatic habitat choked by dense water hyacinth mats is currently much less than during the first 100 years after the arrival of the species. Waterways are kept clear of dense infestations only through extraordinary management efforts involving field crews engaged in full time mechanical removal and biocidal control of E. crassipes. Complete eradication from Florida is impossible.
Potential to Compete With Natives: Water hyacinth is a Category 1 invasive exotic in Florida, capable of altering native plant communities by displacing native species and changing community structures or ecological functions (FLEPPC). Holm et al. (1977) describe Eichhornia crassipes as one of the worst weeds in the world.
The capacity of water hyacinth to invade and overtake aquatic habitat is astounding. Growth rates are explosive and vegetative population doubling can take place in 1-3 weeks (Mitchell 1976, Wolverton and McDonald 1979, Langeland and Burkes 1998).
The species can quickly dominate natural areas and can dramatically alter the species composition, structure, and function of native plant and animal communities (Langeland and Burks 1998).
The suspended root system may account for up to half of the plant biomass. The adventitious roots are clonal plants that break off of the parent to immediately thrive on their own and are also capable of taking root in moist soil in low water conditions.
Possible Economic Consequences of Invasion: Large, dense Eichhornia crassipes mats can degrade water quality and can choke waterways. Plant respiration and biomass decay can result in oxygen depletion and fish kills (FDEP undated).
The documented negative economic impacts of water hyacinth invasion worldwide have included the clogging of irrigation channels, choking off of navigational routes, smothering of rice paddies, loss of fishing areas, increase in breeding habitat available to disease-transmitting mosquitoes, and others (Room and Fernando 1992, ISSG).
The costs associated with removal and maintenance control of water hyacinth are significant.
Barrett S.C.H. 1980a. Sexual reproduction in Eichhornia crassipes (water Hyacinth). 1. Fertility of clones from diverse regions. Journal of Applied Ecology 17:101-112.
Barrett S.C.H. 1980b. Sexual reproduction in Eichhornia crassipes (water hyacinth). II. Seed production in natural populations. The Journal of Applied Ecology 17:113-124.
de Casabianca M.-L. and T. Laugier. 1995. Eichhornia crassipes production on petroliferous wastewaters: effects of salinity. Bioresource Technology 54:39-43.
Flora of North America. 2003. 26:39-41. Published online.
Florida Department of Environmental Protection. Undated. Water hyacinth management - A good example of maintenance control in Florida. FDEP Bureau of Invasive Plant Management Circular 19. 3 p.
Gopal B. and Sharma K.P. 1981. Water-hyacinth (Eichhornia crassipes), most troublesome weed of the world. Hindasia Publications, Delhi, India. 219 p.
Gopal B. 1987. Water hyacinth. Elsevier Science Publishers, Amsterdam. 471 p.
Holm LG, Plucknett DL, Pancho JV, Herberger JP. 1977. The world's worst weeds: Distribution and biology. Honolulu: University Press of Hawaii. 609 pp.
Langeland KA, and KC Burks (Eds.). 1998. Identification and Biology of Non-Native Plants in Florida's Natural Areas. UF/IFAS. 165 p.
Mitchell D.S. 1976. The growth and management of Eichhornia crassipes and Salvinia spp. In their native environment and in alien situations. In: Varshney C.K. amd J. Rzoska (Eds.). Aquatic weeds in southeast Asia. W. Junk Publishers, Netherlands. 396 p.
Ramey V. 2001. Non-Native Invasive Aquatic Plants in the United States: Eichhornia crassipes. Center for Aquatic and Invasive Plants, University of Florida and Sea Grant. Available online.
Room P.M. and I.V.S. Fernando. 1992. Weed invasions countered by biological control: Salvinia molesta and Eichhornia crassipes in Sri Lanka, Aquatic Botany 42:99-107.
Schmitz D.C., Schardt J.D., Leslie A.J., Dray F.A., Osbourne J.A. and B.V. Nelson. 1993. The ecological impact and management history of three invasive alien aquatic plant species in Florida. In: McKnight (Ed.). Biological pollution-The control and impact of invasive exotic species. Indiana Academy of Science, Indianapolis. 261 p.
Wolverton B.C. and and R.C. McDonald. 1979. Waterhyacinth (Eichhornia crassipes) productivity and harvesting studies. Economic Botany 33:1-10.