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Dense E. crassipes mats can overtake and choke water bodies. Photo courtesy UF/IFAS Center for Aquatic and Invasive Plants. Photographer Ann Murray.

Species Name: 
Eichhornia crassipes (Mart.) Solms

Common Name(s):
Water Hyacinth, Common Water Hyacinth, Waterhyacinth, Floating Waterhyacinth, Water-Orchid, Jacinthe D'eau

Synonymy:
Eichhornia cordifolia Gand.
Eichhornia crassicaulis Schltdl.
Eichhornia speciosa Kunth
Heteranthera formosa Miq.
Piaropus crassipes (Mart.) Raf.
And four more.

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).

II.  HABITAT AND DISTRIBUTION 

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.

III. LIFE HISTORY AND POPULATION BIOLOGY

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.

IV.  PHYSICAL TOLERANCES

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).