Water hyacinth
Native to: South America
Water hyacinth was introduced into the U.S. in 1884 at the Cotton States Exposition in New Orleans as an aquatic ornamental plant. It can now be found in freshwater systems throughout the southeast, as well as in California and Washington state. In Florida, where for 100 years water hyacinth had the upper-hand in plant management, it is under maintenance control and not nearly as abundant as it once was. Aquatic plant managers work to keep water hyacinth at their lowest possible levels, in exchange for the rivers and lakes remaining usable.
Water hyacinth grows in all types of freshwaters environments. This plant varies in size from a few inches to over three feet tall. They have showy lavender flowers and the leaves are rounded and leathery, attached to spongy and sometimes inflated stalks. Water hyacinth has dark feathery roots and may be confused with frog’s-bit (Limnobium spongia) which has a somewhat similar appearance.
Water hyacinth has a variety of negative impacts once introduced into a freshwater environment. it forms dense, impenetrable mats which clog waterways, making boating, fishing and almost all other water activities, impossible. It also reduces biodiversity by crowding out native plants at the water's surface and below. Water hyacinth mats also degrade water quality by blocking the air-water interface and greatly reducing oxygen levels in the water, eliminating underwater animals such as fish.
Water hyacinth is a major freshwater weed in most of the frost-free regions of the world and is generally regarded as the most troublesome aquatic plant. Despite its adverse impacts, it has been widely planted as a water ornamental around the world because of its beautiful, striking flowers. Water hyacinth spreads rapidly by producing stolons or "daughter" plants. Water hyacith will never be completely eradicated, however management is necessary to control its rapid growth, as the mats it forms can double their size in 6-18 days.
Water hyacinth is not recommended by UF/IFAS. It is a prohibited plant according to the FDACS Florida Noxious Weed Index and the Florida Prohibited Aquatic Plants List and therefore, illegal to possess. The UF/IFAS Assessment lists water hyacinth as prohibited and it is listed by FLEPPC as a Category l invasive species due to its ability to invade and displace native plant communities.
Water hyacinth should never be introduced into any body of water. It is prohibited by the state of Florida to cultivate, introduce, collect, and transport water hyacinth without a permit.
Very small infestations of water hyacinth may be controlled by handpulling. Water hyacinth thrives in nutrient-rich waters, so reducing nutrient concentrations in impacted waters, may decrease the vigorous growth of this plant.
Mechanical harvestors and chopping machines can be used to remove water hyacinth from the water and transport it to disposal on shore.
Three biological control insects have been imported, studied, and released to control water hyacinth. Together, these insects reduce the size and vigor of water hyacinth and reduce flower and seed production. Individually, however, they are not able to control water hyacinth. Click here to learn more.
Several registered aquatic herbicides provide temporary control of water hyacinth. See: Efficacy of Herbicide Active Ingredients Against Aquatic Weeds to learn more.
