Eichhornia

Scientific name

Eichhornia Kunth.

Common names

water hyacinth, anchored water hyacinth

Family

Pontederiaceae

Could be confused with

Heteranthera, Limnobium, Limnocharis, Monochoria

Native distribution

tropical America, Africa

Species commonly cultivated

Eichhornia azurea (Sw.) Kunth (tropical and subtropical America)

E. crassipes (Mart.) Solms (Brazil)

E. diversifolia (Vahl) Urb. (Central and South America)

E. heterosperma Alexander (Central and northern South America)

E. natans (P. Beauvois) Solms (West Africa, Tanzania, Madagascar)

E. paniculata (Spreng.) Solms (South America)

U.S. Federal Noxious Weed: Eichhornia azurea

Identification: Eichhornia azurea can be distinguished from other Eichhornia by its elongate, fan-like submersed leaves and elongate, anchored floating stem with large obovate, erect leaves with slender petioles.

See Eichhornia azurea disseminule fact sheet.

Adventive distribution

Eichhornia crassipes is introduced into numerous tropical and subtropical countries around the world. Eichhornia paniculata, E. diversifolia and E. azurea have historical records in Texas and Florida, but apparently no extant populations have been substantiated recently in the United States.

Weed status

Eichhornia crassipes is considered one of the world’s most serious aquatic weeds and is a declared noxious weed in many countries. Eichhornia azurea is an aquatic weed on the U.S. federal noxious weed list. Due to the weed status of E. crassipes and E. azurea, several, and in some cases, all species of Eichhornia have been subsequently designated as prohibited imports in various countries (e.g. Australia).

Habit

submersed, emergent or free floating stem or rosette plant

Brief description

Annual or perennial. Stems floating and stoloniferous or creeping, compact and rhizomatous or elongate. Leaves submerged, floating or emergent (or a combination of any two), in basal rosette or cauline, alternate, distichous (2 rows) or spirally arranged, sessile or petiolate, petiole often inflated with aerenchyma in floating plants; submersed leaves linear, emersed leaves ovate to orbicular, venation inconspicuous, parallel to palmate; base rounded to cordate; margin entire. Inflorescence a spike or panicle, subtended by 2 reduced, dissimilar leaves (spathes); lower spathe leaf-like, upper scale-like. Flower zygomorphic; perianth fused, of 6 showy tepals in 2 whorls of 3; lobes unequal, adaxial lobe larger than rest; tepals usually pink to purple with yellow spot on adaxial lobe. Dispersal by numerous seeds or stem fragments; seeds of E. crassipes may be viable in the sediment for 15 years.

Natural habitat

all types of slow flowing or still water bodies

Additional comments

Eichhornia contains seven species, of which five are presently cultivated for aquaria or ponds, and one, E. paniculata, is often a research subject in flower structure genetics.