06/02/08

Eichhornia Crassipes

Eichhornia crassipes
(Mart.) Solms, Pontederiaceae


Present on Pacific Islands? yes
Threat only at high elevations? no
Risk assessment results: Reject, score: 14 (Go to the risk assessment)
Common name(s): [more details]

English: Nile lily, water hyacinth

Fijian: bekabekairaga, dabedabe ne ga, mbekambekairanga, ndambendambe ni nga

French: jacinthe d'eau, pensée d'eau

Hindi: jal khumbe

Japanese: hoteiaoi

Maori (Cook Islands): riri vai

Palauan: bung el ralm

Spanish: aguapey, buchon, calamote, jacinto aquático, jacinto de agua, jacinto de rio, lechuguilla, liro de agua, tarulla

Habit: aquatic herb
Description: "A perennial aquatic herb; stems short, floating or rooting in mud, rhizomatous or stoloniferous, rooting from the nodes; roots long, sometimes dark because of their purple anthocyanin, pendant; leaves in a rosette; petioles spongy, in young specimens short and with a one-sided swelling or inflation but up to 30 cm long when older, tapering and narrowing from the bulbous base to the point of attachment with the lamina; lamina circular to kidney-shaped, glossy smooth, 4 to 15 cm long and wide, acting as a sail in the wind; inflorescence in spikes with about eight flowers, long peduncled, bibracteate, the lower bract with long sheath and small lamina, the upper almost entirely included within the sheath of the lower one, tubular with a small pointed tip (apiculate); flower-bearing part of the rachis up to 15 cm or less long; entire scape may be 30 cm; perianth six-lobed, united below into a narrow tube, lilac, bluish purple or white, the upper lobe bearing a violet blotch with yellow center; stamens six, three long, three shorter, attached to the tube; capsule membranous, three-locular, dehiscent, many-seeded, as many as 50 or so per capsule; seed ovoid, ribbed, 0.5 to 1 mm. The species is distinguished by the almost one-sided swelling or inflation of the petiole, its long peduncled bibracteate spike, and its upper perianth blotched with yellow at the center" (Holm et al., 1977; p. 72).
"Rooted only at flowering time by long slender roots; otherwise floating, with thick, fleshy, more or less horizontal roots; leaves clustered, on bulbously inflated petioles, blades rounded or oblong, up to 3-4 inches wide; flowers showy, pale violet with a spot of bright yellow on the large upper lobe, some forms with pink and yellow flowers, all parts edible" (Stone, 1970; p. 116).
Habitat/ecology: Freshwater lakes, ponds, marshes, ditches, canals, slow-moving streams. "It is an aquatic floating weed. It does not tolerate brackish water (Holm et al., 1977; pp. 72-77) and salinity can limit or modify its distribution. For example, water hyacinth, which accumulates in the coastal lagoons of West Africa during the wet season, is reduced in those areas which become saline during the dry season. Growth by water hyacinth is favored by nutrient rich water, in particular by nitrogen, phosphorus and potassium" (Ecoport). "High growth rates mean populations can quickly form thick mats on the water surface. This makes passage by boats difficult, chokes irrigation channels, pollutes water and provides breeding grounds for disease-carrying insects. The natural beauty of areas is also degraded as native plants, birds and fish are displaced." (Smith, 2002; p. 82).
In Hawai‘i, "introduced as an ornamental, now naturalized and locally abundant in standing or slow-moving water such as ponds and sluggish streams at low elevations" (Wagner et al., 1999; pp. 1604-1606). In Fiji, "a locally abundant adventive, occurring near sea level (but elsewhere up to an elevation of 1,600 m or higher)" (Smith, 1979; pp. 175-176). In New Caledonia, "peu cultivée à présent, existe en masses serrées là où des rivières à courant faible ou des mares lui offerent des stations favorables mais n'obstrue pas les cours d'eau autant qu'en d'autres pays tropicaux" (MacKee, 1994; p. 118). In New Zealand, "An established escape from ponds and aquaria, now eradicated from many localities. E. crassipes was originally introduced as an ornamental, but it both accidentally escaped from cultivation and was deliberately planed, and by 1950 was established and troublesome in dams, ponds, swamps, slow-moving streams and river cut-offs in the Auckland Province" Possession of the plant in New Zealand is illegal (Healy & Edgar, 1980; p. 60).
Propagation: "Water hyacinth reproduces vegetatively by means of stolons which, together with solitary plants or drifting mats, are readily distributed by water currents, wind, boats and rafts. The plant also produces vast quantities of long-lived seed and persistence and spread by this means can be very significant (Sculthorpe 1971)." (Ecoport). "Spread throughout its range by intentional introductions as an ornamental" (Smith, 2002; p. 82).
Native range: Amazon basin, now introduced and cultivated in most warm countries.

More details http://www.hear.org/pier/species/eichhornia_crassipes.htm