Water Hyacinth, a weed of tropical and subtropical waters. It is related to the true hyacinth. Growths of water hyacinth are troublesome to navigation in inland waters of Florida, Central and South America, central Africa, Southeast Asia, and northern Australia. Efforts to control the growths have resulted in only temporary relief. In India, the plants have been used for making paper and pressed board.

The water hyacinth has smooth, nearly round leaves, up to six inches (15 cm) wide. The loose clusters of pale violet, orchidlike blossoms have blue and yellow markings. The leaf stalks have bladderlike bases that serve as floats for the blossoms. The roots are of two types. One type grows along the water surface, like runners, producing new plants. The other type is heavily covered with long root hairs that droop in the water like plumes. The plants multiply by means of the root runners. A central plant is soon surrounded by other plants until a large floating island is formed.

The water hyacinth is Eichhornia crassipes of the family Pontederiaceae.