Hydrilla, Hydrilla verticillata, is an aquatic weed not native to Florida but widespread within the state. It is a submerged, rooted (usually) perennial with long, sinewy branching stems that often reach the surface and form dense mats. The stems are covered in small, pointed, often serrate leaves arranged in 4-8 whorls. Leaf midribs are often reddish with one or more sharp spines. Small pale subterranean tubers occur attached to the roots. Small white flowers grow above the water line on stalks (Godfrey and Wooten 1979, Illinois-Indiana Sea Grant College Program undated).H. verticillata exhibits a degree of penotyoic plasticity (variable physical appearance) in response to age, habitat conditions, and water quality (Kay 1992). Branching is generally sparse in submerged portions of the plant, tending to become profuse at the surface (Langeland 1996).