Alligator weed is a rooted, vining plant that forms mats extending outward from shorelines. It was introduced into the U.S. from South America in the early 1900s.
It has shiny green, elliptical leaves that are opposite and simple up to 4 inches in length. The flowering stems are upright, and the plant produces a white flower with five petals, blooming from April through October.
They can multiply into incredibly dense mats and can clog waterways and prevent shoreline access. The alligatorweed flea beetle, Agasicles hygrophila, also from South America, has been successfully introduced as a natural biological control on alligator weed.