water hyacinth, water-hyacinth, common waterhyacinth, Eichhornia speciosa Kunth, Piarpus crassipes (Mart.) Britton, Heteranthera formosa, Eichhornia crassipes (Mart. and Zucc.)

Habit: Free-floating, perennial, herbaceous, aquatic forb

Roots: Short rhizomes, typically feathery and black to purple

Stems: Short and unbranched; multiple ramets, or daughter plants, form on an horizontal stolon from axillary buds

Leaves: Sessile and petiolate leaves, with thick, glossy leaves (12-15 cm wide) that are ovate to cordate to reniform. Spirally-alternating leaf arrangement from central growing point (monopodial) with older, sessile leaves oppositely arranged. Floating petiolate leaves are held above the water by bulbous, spongy inflated petioles (to 30 cm long) when plants grow in relatively open conditions. Petioles are thinner and more vertical when growing under crowded conditions (Center and Spencer 1981; Gettys 2014; Penfound and Earle 1948).

Flowers: Showy lavender flower spikes (sometimes pale blue to white) bloom summer to early fall and are insect pollinated; individual flowers are 4-6 cm wide and have six lobes with the upper lobe enlarged and a central yellow spot surrounded by dark blue.

Fruits: Pollinated flowers produce capsules containing many seeds (Barrett 1980).

Look-a-likes: Only Pontederia crassipes have inflated petioles. Limnobium spongia have a similar leaf shape but with more prominent veination and more uniform, less tapered petioles. Heteranthera limosa, H. reniformis, and H. rotundifolia have similar leaf shapes but the flowers are smaller and have three stamens.

Once introduced to a new region, the plant quickly establishes and spreads.  In the absence of sustained freeze, the plant grows as a perennial.  In its northern range, the plant grows as an annual, where it is either re-introduced or germinates from seed.  Long-term exposures (2-4 weeks) to temperatures at or near freezing are required to significantly reduce P. crassipes populations (Owens and Madsen 1995; Russell 1942). The plant has a low tolerance for saline waters.  Plants grown in water containing 3% seawater exhibited significant leaf necrosis after 28 days (Penfound and Earle 1948). 

Dense, floating mats of P. crassipes and the subsequent build-up of organic detritus in the mat create an environment that supports the growth of emergent aquatic and terrestrial species, including woody species such as Salix spp. and Cephalanthus occidentalis.  These floating islands (also referred to as tussocks, sudds, and flotants), accelerate succession and create concern for navigation and infrastructure (Penfound and Earle 1948; Russell 1942). 

Pontederia crassipes reproduces vegetatively through the production of ramets and an abundance of seeds.  Flowers are known to be pollinated by a number of insects, most notably the introduced honey bee (Aphis mellifera L.) (Penfound and Earle 1948; S.C.H. Barrett).   Seeds remain dormant in the hydrosoil until exposed to a drying event (Penfound and Earle 1948; Gettys 2014). Pontederia crassipes can double its population in as little as two 2 weeks, creating an enormous amount of floating biomass (Penfound and Earle 1948).  One hectare of healthy P. crassipes can weigh as much as 415 metric tons (Schardt 1997).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic	Beneficial

Eichhornia crassipes grows in thick mats that reduce the light and oxygen availability in the water (Ivanov 2006). After removing E. crassipes from Lake Victoria by cutting, there was a significant increase in dissolved oxygen (Osumo 2001). In Africa, Eichhornia crassipes can be detrimental to water availability due to its high rate of evapotranspiration and its ability to take advantage of scarce water reserves, resulting in an annual loss of 7 billion m3 of water from the Nile River (De Groot 1993, Padilla and Williams 2004). In China, E. crassipes has exacerbated water pollution by absorbing heavy metals and releasing them at death (Jianqing et al. 2001).

In Lake Okeechobee, E. crassipes displaced native bulrush and shaded out native submerged plants that provide important habitats for fish, waterfowl, and other animals (University of Florida 2013). In Caohai and Dianchi lakes in Yunnan province, southwestern China, E. crassipes competed with native plants for water, nutrients, and space, and contributed to the reduction in native plant diversity (Jianqing et al. 2001).

Eichhornia crassipes can potentially alter predator-prey relationships. In San Joaquin Delta, California, insect densities where lower in patches of E. crassipes and there was a difference in insect composition between E. crassipes and the native pennywort (Hydrocotyle umbellata)(Toft 2000). Non-native introduced amphipods such as Crangonyx floridanus were more abundant in E. crassipes than in the native pennywort, and are not frequently consumed by fish. Fish preyed heavily on native amphipod Hyalella azteca that was more abundant in the native pennywort. It is suggested that the presence of E. crassipes may influence native invertebrate community assemblages.

Eichhornia crassipes has the potential for high socio-economic impact if introduced to the Great Lakes.

Eichhornia crassipes can pose a risk to human health by providing a habitat for mosquitos, and may increase the risk of mosquito-borne diseases (Jianqing et al. 2001, Mailu 2001). This species has reduced water availability in Lake Victoria Basin, which led to social conflicts over the lack of clean water (Mailu 2001). In addition, the infestation of E. crassipes resulted in increased transportation costs, blockage of irrigation canals, and difficulties in electricity and water extraction. Due to E. crassipes infestation, the Kenyan port of Kisumu reported a 70% decline in economic activities. This species can impact recreational fishing by making it difficult to access fishing grounds and preventing boating (Mailu 2001, Richardson and Wilgen 2004). 

In Benin, the infestation of E. crassipes was estimated to significantly reduce the annual income of the villagers, who relied on fishing and trade for an income (De Groote et al. 2003). Biological control of the infested waters in Benin was estimated to be US $2.09 million.

Eichhornia crassipes has the potential for moderate beneficial impact if introduced to the Great Lakes.

Eichhornia crassipes is an ornamental plant used in water gardens. Eichhornia crassipes has the potential to be used for bioethanol and biogas production, electricity generation, industrial uses, animal feed, or agriculture (Jafari 2010, Malik 2007). It may be utilized for wastewater treatment or heavy metal remediation (Pinto et al. 1987).