The water hyacinth (Eichhornia crassipes) has the reputation as the worst invasive aquatic weed in the world, according to the Center for Aquatic and Invasive Plants. One single acre of water hyacinth can weigh as much as 200 tons, which explains why the water hyacinth clogs up waterways. Swimmers, boaters and anglers all feel the effects of these waterway-choking weeds, which despite their negative aspects, do have some benefits to the environment.
The leaves of water hyacinth have a round or kidney shape and are from 1 to 5 inches wide. The leaves are a shiny bright green and can rise as far as 3 feet over the surface of the water. The flower is quite attractive, growing on a spike as tall as a foot on a stalk that can reach 20 inches long. The six-petaled flowers are a lavender-blue mix or white, with a patch of yellow on the upper petal. The feathery roots are black to dark purple and hang freely beneath the plant. The seeds occur in a capsule.
The water hyacinth is native to South America. After its introduction to the southern United States in the late 1800s, the plant spread quickly from Virginia to Florida and west to Texas. Water hyacinth is now common throughout warm weather areas of the world, existing in India, New Zealand, Australia, Asia, Africa and Central America. Water hyacinth grows in swamps, ponds and lakes, slow-moving stretches of rivers, ditches, backwaters and streams. The plant requires water rich in nutrients, as it does not put down any roots into the bottom, but rather develops dangling roots. The water hyacinths link together and create floating rafts of plants.
The dense growth of water hyacinths prevents a good flow of water in rivers and streams, and it can significantly reduce the oxygen levels in the water. Native water plants cannot grow under these rafts of weeds, but mosquitoes may breed in the conditions they create. The plants which many species of aquatic creatures depend upon for food will not grow, affecting the ecosystem in still another manner.
Water hyacinth cannot make grow in the northern United States because it cannot withstand cold temperatures. The minimum temperature at which water hyacinth can grow is about 54 degrees Fahrenheit. The highest temperatures water hyacinth can stand are 92 to 95 degrees Fahrenheit. The plant thrives when the water temperature ranges from 77 to 86 degrees Fahrenheit.
The "National Audubon Society Field Guide to Wildflowers" says that not every facet of the water hyacinth is negative. The plant can remove nutrients from waters that actually possess too many. If periodically harvested mechanically, the water hyacinth can benefit these waterways. The plant can also take pollutants and heavy metals out of the water as well.