Eichhornia

Water hyacinth are free-floating perennial aquatic plants belonging to the genus Eichhornia. Native to South America, they have been widely introduced throughout North America, Asia, Australia and Africa. In many areas water hyacinth is an important and pernicious invasive species.

First introduced to North America in 1884, common water hyacinth (Eichhornia crassipes) is a vigorous grower known to double its population in two weeks. An estimated 200 tons of hyacinth per acre once choked Florida's waterways, although the problem there has since been mitigated. When not controlled, water hyacinth will cover lakes and ponds entirely; this dramatically impacts water flow, blocks sunlight from reaching native aquatic plants, and starves the water of oxygen.

With broad, thick and glossy ovate leaves, water hyacinth may rise some 90 centimetres (3 feet) in height. The large (up to 20 cm or 8") leaves are supported above the water surface by long, spongy and bulbous stalks. The feathery, freely hanging roots are purplish black. An erect stalk supports a single spike of 8-15 conspicuously attractive flowers, mostly lavender to pinkish in colour with six petals. When not in bloom, water hyacinth may be mistaken for the native frog's-bit (Limnobium spongia).

One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, eventually forming daughter plants. They may also reproduce via seeding.

Directly blamed for starving subsistence farmers in Papua New Guinea and Australia, water hyacinth remains a major problem where effective control programmes are not in place. The plants create a prime habitat for mosquitos, the classic vectors of disease, and a species of snail known to host a parasitic flatworm which causes schistosomiasis (snail fever).

As chemical and mechanical removal is often too expensive and ineffective, researchers have turned to biological control agents to deal with water hyacinth. The effort began in the 1970s when USDA resarchers released into the United States three species of weevil known to feed on water hyacinth: Neochetina bruchi, N. eichhorniae, and the water hyacinth borer (Sameodes albiguttalis). Although met with limited success, the weevils have since been released in more than 20 other countries.

See also: List of garden plants, list of introduced species

External links

• Water hyacinth in Africa and the Middle East: A survey of problems and solutions

Referenced By