Family: Hydrocharitaceae, Frog's-bit view all from this family

Description Introduced. An invasive, submersed aquatic plant that forms numerous long stems, up to 25' (7.5 m) long, with whorls of leaves along their length; rhizomes produce swollen, light brown tubers.
Flowers: small white flowers on long stalks.
Leaves: whorls of 4-8 saw-toothed, lance-shaped leaves ring the stem; midrib toothed or spiny.
Height: 25' (7.5 m).

Habitat Fresh water, both still and moving.

Range Introduced in the United States and established in California, Washington, Texas, the Southeast, and the Atlantic coast states north to Massachusetts.

Discussion Hydrilla was introduced into the United States as an aquarium plant. It very quickly spreads in fresh water, forming dense mats from the bottom to the water surface, and is said to be able to grow up to 10 inches in a day. Hydrilla is classified as a noxious weed by the U.S. government as well as many individual states. The U.S. Army Corps of Engineers is studying options for biological control of Hydrilla with the use of certain species of insects and fish that feed on or otherwise destroy the plants' reproductive capacity.