The water hyacinth is known as the world’s worst aquatic plant. Native to the tropical and sub-tropical of South America it is a free-floating hydrophyte or perennial aquatic plant. It has become naturalized in many warm areas of the world: Central America, California and southern states, Africa, India, Asia, Australia and New Zealand. Its leaves are thick, glossy and ovate that may rise above the surface water by one meter in height and are 10 to 20 cm across. The stalks are long, spongy and bulbous with roots that are feathery, freely hanging and purple-black. One erect stalk supports a single spike of 8 to 15 conspicuously attractive flowers. The flowers are mostly lavender to pink in color with six petals. Quite often when not in bloom it is mistaken for a frog’s-bit.
The water hyacinth is one of the fastest-growing plants know. It reproduces primarily by way of runners or stolons which eventually form daughter plants with each plant producing thousands of seeds each year. The seeds will remain viable for more than 28 years.
Water hyacinths grow over wetlands from lakes, streams, ponds, waterways, ditches and backwater areas. They obtain their nutrients directly from the water and prefer nutrient-enriched waters.
The water hyacinth was first introduced into the United States at the World’s Industrial and Cotton Centennial Exposition of 1884 – 1885 in Louisiana. It made its way to Florida through a visitor to the Exposition who upon returning to Florida released the plants into the St. John’s River. It rapidly spread to neighboring states.
Controlling the growth has been difficult at best. While there has been a success with using the aquatic herbicides 2,4-D or diquat, mechanical control by harvesting is largely ineffective for large-scale control. Florida has been using this method for over 100 years and it is very expensive.
Three insects were released for biological control. The insects included two weevils and a moth. Unfortunately, they did not see the large-scale reductions of the water hyacinth hoped for. There was a reduction in plant height and a decreased in the number of seeds produced as well as a decrease in the seasonal growth of the plants. With the decreased growth, this allowed for better boat access into the plant mats and a reduction in the use of herbicides. It also resulted in fewer plant problems.