EichhorniaCrassipes01

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E. crassipes is a free-floating aquatic macrophyte growing generally to 0.5 m in height but to nearly 1 m in height in some southeast Asian locations (Gopal 1987). E. crassipes forms dense, floating mats. As a free-floating plant, all its nutrients come from the water column (Sculthorpe 1985). Leaves are thick, waxy, rounded, and glossy and rise well above the water surface on stalks. The leaves are broadly ovate to circular, 10-20 cm in diameter, with gently incurved, often undulate sides. Leaf veins are dense, numerous, fine and longitudinal. Leaf stalks are bulbous and spongy. The stalk is erect, to 50 cm long, and carries at the top a single spike of 8-15 showy flowers. The flowers have six petals, purplish blue or lavender to pinkish, the uppermost petal with a yellow, blue-bordered central splotch. Water hyacinth reproduces vegetatively by short runner stems (stolons) that radiate from the base of the plant to form daughter plants, and also reproduces by seed. Its roots are purplish black and feathery (Gopal 1987).

E. crassipes forms a shoot consisting of a branched, stoloniferous rhizome, 6 cm in diameter and up to 30 cm in length, with several short internodes. Each node bears a leaf and roots. Auxiliary buds, which can also form stolons, grow at an angle of 60 degrees from the rhizome and remain at that angle or bend upward in dense stands, or become horizontal in open stands. Plants on the edge of a mat form stolon buds while those in the middle may not. Stolons are purplish violet and extend up to 50 cm or more in length and are highly variable in diameter (Gopal 1987).

Leaves form as the auxiliary bud grows, rupturing a tubular leaf-like structure called a "prophyll." As the internode between the first leaf and the prophyll elongates, roots are produced at the node bearing the primary leaf. Foliage leaves are formed after. Foliage leaves are petiolate with a glossy sheen, and are arranged spirally, appearing to be in a rosette. Each leaf consists of a petiole, isthmus (between petiole and blade) and blade. The petiole bears a large membranous stipule, which forms a sheath around the next younger leaf. Petioles are spongy and measure up to 5 cm in diameter and 30-50 cm in length (maximum 125 cm). They may be elongated, swollen in the middle and tapering towards the blade or they may form a bulbous float (Gopal 1987) containing air-filled lacunate tissue (Sculthorpe 1985).

As much as 50% of a single water hyacinth’s biomass can be roots. Roots are adventitious and fibrous, 10-300 cm in length. As many as 70 lateral roots per cm give the roots a feathery appearance. They are dark violet to bluish or pinkish violet (though whitish if grown in total darkness) and contain soluble pigments, including anthocyanins that may protect the root from herbivory (Gopal 1987).

Flowers are borne terminally on a lavender spike on an elongated peduncle and are subtended by two bracts. The lower bract has a distinct blade. Each spike has 4-25 flowers (maximum 35) with 8-15 being the most common. Flowers are sessile. The perianth tube is 1.5-1.75 cm long with a green base and pale top. Tepals are ovate to oblong, thin, lilac and up to 4 cm long. The posterior tepal (labellum) has a central bright yellow diamond-shaped region surrounded by a deep blue border with bright red radiating lines. When young, this labellum has a green spot. There are six stamens (sometimes 5 or 7) having curved filaments with glandular hairs. Three are small and close to the perianth tube. Anthers are violet and measure 1.4-2.2 mm long (Gopal 1987).

The gynoecium is tricarpellary and superior. The ovary is nearly conical and produces approximately 500 ovules. The style is variable in length and bears a nearly capitate stigma with three closely appressed lobes. Sometimes the stigma is trifid and may be longer, shorter or intermediate in length compared to the stamens. This heterostyly makes E. crassipes trimorphic (Gopal 1987).

The fruit is a thin-walled capsule enclosed in a relatively thick-walled hypanthium developed from the perianth tube. Mature seeds can number 450 per capsule, are 4 x 1 mm, with an oval base and tapering apex. The coat has 12-15 longitudinal ridges (Gopal 1987).

E. crassipes can be distinguished from most other floating and mat-forming aquatic plants by its highly glossy leaves, the almost one-sided swelling of its petioles (Holm et al. 1991), and its showy lilac flowers. E. crassipes can float freely, unlike its congener E. azurea which must root to the substrate and is therefore confined to shallow ponds and the edges of lakes and rivers (Barrett 1989). E. azurea is a USA federal noxious weed which has been imported from South America to decorate ponds and occasionally escaped into local environments. It often produces a much more showy inflorescence than E. crassipes, one sometimes carrying more than 60 flowers (Gopal 1987).

Other interest: named for 19th century Prussian politician J.A.F. Eichhorn; native to tropical So. America and naturalized throughout the tropics and subtropics; attractive blue-black roots; may be invasive in native and warm areas, especially if water is nutrient rich, clogging waterways and necessitating chemical or mechanical removal; roots extract heavy metals from water making it useful as a water purifier; related to the Peacock Hyacinth, E. azurea, which spreads in the shape of a peacock's tail to 6' across