[plants.ifas.ufl.edu] South America Native, Habitat, Habits: Native to: South America. Alligatorweed was accidentally introduced into Florida in 1894 in ships' ballast water and can now be found growing throughout the state. This rooted perennial plant can grow in various habitats, although it is usually found in water. It forms sprawling mats over deep rivers or along shorelines and can be a pest on land. (link added by Mary Ann Machi)