Alligatorweed is an emergent or rooted floating invasive that invades aquatic areas throughout the southern portions of the United States. The opposite leaves are non-succulent. The white flowers occur in short, headlike spikes. Alligatorweed roots in wet soils or shallow water and grows out into waterways. The floating mats expand along the surface. Alligatorweed can also grow terrestrially, forming smaller, tougher leaves. The thick mats can displace native vegetation, clog waterways, restricts oxygen levels of water, increases sedimentation, interferes with irrigation, and prevents drainage. Alligatorweed is native to South America and was first introduced into the United States around 1900.