Water Hyacinth (Eichornia crassipes)

General Information About Water Hyacinth (Eichornia crassipes)

Water hyacinth (Eichornia crassipes and related species) has been called the worst aquatic plant in the world! It is native to South America, but has been naturalized in most of the southern United States and in many of the world's subtropical and tropical climates.

Water hyacinth plants have a tremendous growth and reproductive rate and the free-floating mats cause substantial problems. Millions of dollars are spent each year in the United States for its management. Water hyacinth has been widely distributed because of the beauty of its large, purple to violet flowers.

Water hyacinth has not been found in the wild in Washington, but it is sold as an ornamental plant in plant nurseries. Although it is thought that water hyacinth cannot survive Washington's winters, its presence as an ornamental makes it possible for escape and growth in the wild. Water hyacinth does survive freezing conditions in other states where it is established and it may be possible for this plant to survive western Washington's relatively warm winters.

Growth Habit

Water hyacinth can form impenetrable mats of floating vegetation. It reproduces by seeds and by daughter plants which form on rhizomes and produce dense plant beds. In one study, two plants produced 1,200 daughter plants in four months. Individual plants break off the mat and can be dispersed by wind and water currents. As many as 5,000 seeds can be produced by a single plant and these seeds are eaten and transported by waterfowl. Seedlings are common on mud banks exposed by low water levels.

Management

Water hyacinth is controlled through a number of methods including harvesting, aquatic herbicides, and biological control agents. In Washington the best way to manage water hyacinth is to prevent it from becoming established. If you purchase water hyacinth at a local nursery, do not dispose of excess plants by throwing them into a lake, river, stream, or drainage ditch! A number of water hyacinth plants have been found in drainage ditches in the Longview/Kelso area in southwestern Washington. It is thought that these plants have been discarded by somebody cleaning a backyard pond. Dispose of all excess plants on a compost heap and away from water. Also do not purchase water hyacinth and deliberately plant it into your lake. This is asking for trouble.

Identification

Water hyacinth are distinctive-looking plants.

They are floating plants with round to oval, shiny green leaves up-to-ten inches in diameter, although smaller leaves are common.
Leaves are held upright so they act like sails.
The leaf stalk is thick and spongy and helps to keep the plant buoyant.
A mass of fine roots hang in the water underneath the plant.
The flowers are large (2-3 inches) and attractive. They are blue-purple or lilac-colored with a yellow spot.

Another tropical floating-leaved nursery plant, called water lettuce, may be mistaken for water hyacinth. However, water lettuce doesn't have showy flowers and has large "ribbed" leaves. Water lettuce is much less cold-tolerant than water hyacinth and is not thought able to survive in cold climates.

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