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.

Eichhornia azurea
Eichhornia azurea
(anchored waterhyacinth)

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Eichhornia azurea (Sw.) Kunth

Common name: anchored waterhyacinth

Synonyms and Other Names: Eichhornia aquatica, Piaropus azureus, Piaropus tricolor, Piaropus undulatus, Pontederia aquatica, Pontederia azurea, Pontederia tumida

rooted waterhyacinth, saw-petal waterhyacinth.

Taxonomy: available through www.itis.govITIS logo

Noxious: This species is listed by the U.S. Department of Agriculture as a noxious weed.


Habit: rooted, floating-leaved, aquatic perennial with roots typically fixed in mud (Barrett, 1988).

Stems/roots: stems, which can grow up to 8 m in length, form dense stands which can grow to 50 m in width (Agostinho et al., 2007).roots typically vary in length, ranging between 5-100 cm (Padial et al., 2009).

Their leaves can be submerged, emergent, floating, or a combination (Gopal, 1987). Eichhornia azurea’s leaves are alternate on the stem; petiolate leaves are emersed, blade round (7-16 x 2.3-16 cm) with stipule 7-13 cm, and an uninflated petiole (11-25 cm) (Horn, 2002). The leaves of E. azurea grow larger in lotic environments and smaller in lentic environments (Pagioro and Thomaz, 1999).

Flowers are held on erect stems between 8-12cm and bloom for one day (Horn, 2002). Flowering occurs from summer to fall, with 7-50 flowers per stem, some stems carrying over 60 flowers (Gopal, 1987). Eichhornia azurea’s flowers are showy, mauve-blue and white with purple cores and a yellow distal spot (Horn, 2002; Barrett, 1988)., Eichhornia azurea’s style lengths range between 13-15 mm with upper stamen whorls ranging from 17-20 mm in length (Horn 2002; Barrett, 1978). Their proximal stamens range between 15-29 mm with anthers between 1.2-2.3 mm (Horn 2002).Size: Stem length varies and can be shorter than 5 cm in the younger portions of the stems and up to 1 m in the older portions (Padial et al., 2009). The plant can grow to a height of 1 m (Gopal, 1987).

Native Range: Native to Central America, the Caribbean, and regions of South America (Barrett, 1988). It has been reported that E. azurea is widely present in Puerto Rico (Liogier and Martorell, 1982). Eichhornia azurea is particularly common throughout various aquatic habitats in lowland South America, including the Amazon, the Pantanal wetlands, and the Paraná river systems (Bianchi et al., 2000).

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

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Eichhornia azurea are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA193119311Lower Sacramento
MS200520051Middle Pearl-Strong
PR198219821Eastern Puerto Rico
TX196719671South Laguna Madre
VA200920091South Fork Shenandoah

Table last updated 6/25/2024

† Populations may not be currently present.

Ecology: Typical climate types for E. azurea range between tropical rainforest/monsoon to warm temperate (Barrett, 1988). The mat-forming, long-lived perennial is commonly found in large, permanent water bodies with slow-moving water such as rivers, marshlands, and lakes (Barrett 1978; Barrett, 1988). The roots at the nodes remain in contact with the water surface and provide additional structural integrity to littoral regions (Agostinho et al., 2007).

Average seeds per fruit have shown to depend on whether the flowers are mid-styled (40.09 seeds per fruit), or long-styled (27.24 seeds per fruit) (Cunha and Fischer, 2009). The style of a flower is the stalk of the pistil that connects the ovary to the stigma (NCSU, 2021). Each seed is winged, 1.5-2.6 mm long and 0.3-0.9 mm wide (Horn 2002; Sher, 2009). It is primarily pollinated by butterflies and bees (Horn, 2002).

The  roots of E. azurea create underwater shelter in its native range, and provides habitat and a food source (in the form of algae growth) for fishes and invertebrates (Agostinho et al., 2007; Carniatto et al., 2012; Dibble and Pelicice, 2010). Because E. azurea provides structural heterogeneity in its aquatic environments, the rate and efficiency of predation is affected in those environments. An experimental study in its native range to evaluated the effect E. azurea's submerged roots have on predator– prey interactions used Red-eye Tetras (Moenkhausia sanctaefilomenae) as a predator and an ostracod (Cypricercus sp.) and chironomid (Chironomus sp.) as the prey, found that E. azurea roots resulted in increased shelter for both prey types (Padial et al., 2009). A similar conclusion was found in a different study analyzing the predation of Ray-finned fish (Serrapinnus notomelas). It was concluded that the complex structure of E. azurea roots led to the increased density of S. notomelas within the ecosystem, as it provides more protection for the species against predators (Camiatto et al., 2012). Echhornia azurea alters the nutrient concentrations in the water due to high absorption (Castro et al. 2016). A study conducted in the Ivinhema River investigated the fish communities associated with drifting E. azurea macrophyte mats. It was suggested that E. azurea mats provide a dispersal vector for several fish communities as various fish species protect themselves from predators by utilizing the dense macrophyte mats. Fish species' ability to guard themselves against the high risk of predation, along with their reproduction and recruitment of new individuals to their stocks, has resulted in E. azurea acting us an unintentional dispersal vector (Bulla et al., 2011).

Means of Introduction: Through human mediation, E. azurea has spread from South America and established itself as a noxious aquatic weed in Central America and parts of the Caribbean (Barrett, 1988). Although specific vectors are undocumented, boats have been previously linked to the dispersal of exotic weeds over long distances (Johnstone et al., 1985).

Status: Eichhornia azurea is considered native to South America, Central America, Mexico, and Jamaica. It is introduced to Puerto Rico, Rankin County, Mississippi, Augusta County, Virginia, and Columbia county, FL (USDA NRCS, 2021).

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


Eichhornia azurea’s roots have been observed to alter its surrounding habitat. In one study, their roots led to structural heterogeneity that significantly affected Red-eye Tetra’s (Moenkhausia sanctaefilomenae) habitat use and overall behavior. The presence of E. azurea has amplified periphyton, and organic matter richness in its environment. Considering that these are the two primary food supplies for most of the aquatic micro invertebrates, it is suspected that a combination of both the structural complexity of E. azurea's roots along with the consequent food supply is why such a high richness and abundance of macroinvertebrates were observed in the study (Silva and Henry, 2013). Consequently, it was found that richness of macroinvertebrates intrinsic in E. azurea was highest among all other macrophytes in all studied lakes. The dominance of macroinvertebrates communities associated with E. azurea led to a decrease in dissolved oxygen levels within the habitat, decreasing fish species diversity (Silva and Henry, 2013).
There is very little documented impact literature for Eichhornia azurea, but there is more documentation of the impacts of the closely related Eichhornia crassipes.

Remarks: Because E. azurea has a strong absorption capacity for iron and copper, it can be used to identify metal contamination in water habitats (Laybauer and Ortiz, 1999). Eichhornia azurea is closely related to one of the world’s most destructive aquatic weeds, the common water hyacinth (Eichhornia crassipes) (Barrett, 1978).

References: (click for full references)

Silva, C.V., and R. Henry. 2013.Aquatic macroinvertebrates associated with Eichhornia azurea (Swartz) Kunth and relationships with abiotic factors in marginal lentic ecosystems (São Paulo, Brazil). Brazilian Journal of Biology (73) 1 149-162.

Author: Wishah, L., and C.R. Morningstar

Revision Date: 8/30/2023

Citation Information:
Wishah, L., and C.R. Morningstar, 2024, Eichhornia azurea (Sw.) Kunth: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=2758, Revision Date: 8/30/2023, Access Date: 6/25/2024

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.


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Citation information: U.S. Geological Survey. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [6/25/2024].

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