Eichhornia - Water hyacinth

The seven species of water hyacinths comprise the genus Eichhornia. Water hyacinth are free-floating perennial aquatic plants native to tropical South America. With broad, thick, glossy, ovate leaves, water hyacinths may rise above the surface of the water as much as 1 meter in height. The leaves are 10-20 cm across, and float above the water surface. They have 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.

One of the fastest growing plants known, water hyacinth reproduces primarily by way of runners or stolons, which eventually form daughter plants. It also produces large quantities of seeds, and these are viable up to thirty years. The common water hyacinth (Eichhornia crassipes) is a vigorous grower known to double its population in two weeks.


Water hyacinths have been widely introduced throughout North America, Asia, Australia and Africa. For example, they can be found in large water areas in Louisiana, or in the Kerala Backwaters in India. In many areas they, particularly E. crassipes, are important and pernicious invasive species. First introduced to North America in 1884, an estimated 50 kilograms per square metre of hyacinth 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, often leading to fish kills (or turtles). The plants also 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). Directly blamed for starving subsistence farmers in Papua New Guinea, water hyacinth remains a major problem where effective control programs are not in place. Water Hyacinth are often problematic in man-made ponds if uncontrolled.


Species
Eichhornia crassipes commonly known as Common Water Hyacinth is an invasive species of plant, which is native of Amazon basin. This plant is also used like a medicinal plant. The plant was introduced by Belgian colonists to Ruanda to beautify their holdings and then advanced by natural means to Lake Victoria where it was first sighted in 1988 There, without any natural enemies, it has become an ecological plague, suffocating the lake, diminishing the fish reservoir, and hurting the local economies. It impedes access to Kisumu and other harbors.

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