Disclaimer:

The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: common water-hyacinth

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

Taxonomy: available through www.itis.gov

Identification: According to Pellegrini et al. (2018) [Figure 7]:

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.

Size: Up to 1 m in height

Native Range: South America (Brazil)

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Pontederia crassipes is a fast growing, troublesome aquatic plant with global distributions in tropical and subtropical areas of the world (Center and Spencer 1981; Penfound and Earle 1948). The showy, attractive lavender flowers precipitated this worldwide distribution. 

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).

Means of Introduction: Sold as an ornamental for fish ponds; sometimes escapes or is intentionally introduced into larger water bodies such as lakes and reservoirs. 

Status: Populations in the southeastern (North Carolina to Texas) and southwestern (California and Arizona) US remain established (including Guam, Hawaii, Puerto Rico, and the Virgin Islands), while those in northern states (Washington to Colorado to New York) likely do not overwinter.

Impact of Introduction:

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

Ecological	Economic	Human Health	Other

Since its introduction, P. crassipes has notoriously interfered with navigation, triggering the 55th Congress, through the Rivers and Harbors Act of 1899, to authorize the U.S. Army Corps of Engineers to address the problem (Schardt 1997) after commercial commerce was impeded by P. crassipes on the St. Johns River (Webber 1897).  In one instance, 65 feet of a railroad trussel across Rice Creek near Palatka, FL was destroyed in 1894 by build-up of waterhyacinth.

Pontederia crassipes can develop into dense floating mats of substantial biomass, intertwined with stoloniferous offshoots, and often associated with the growth of opportunistic emergent macrophytes, resulting in this introduced plant being labeled one of the “world’s worst weeds” (Holm et al. 1997; Lowe et al. 2000).  The free-floating nature of the plant only exacerbates its problematic standing because the populations can move with water flow and wind. Recreational use of waters infested with this plant are greatly reduced. Pontederia crassipes can also impede drainage, creating backwater flooding conditions.

Water quality and wildlife habitat can be greatly affected, reducing dissolved oxygen levels under mats by an order of magnitude and covering the water surface with an impenetrable barrier (Penfound and Earle 1948).  These dense surface mats shade out desirable submersed aquatic plants and create a safe breeding environment for mosquitoes (Savage et al. 1990).

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Other Resources:
Pontederia crassipes | UF/IFAS Center for Aquatic and Invasive Plants

US Army Corps of Engineers - Jacksonville District Aquatic Plant Control Program

US Fish and Wildlife Service Ecological Risk Screening Summary for Eichhornia crassipes

Author: Pfingsten, I.A., D.D. Thayer, C.C. Jacono, M.M. Richerson, and V. Howard

Peer Review Date: 2/25/2016

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.