Hydrilla verticilata is the scientific name for this noxious invader from afar. No-one knows for sure where hydrilla is native to, yet its believed that it probably originated somewhere in southeast asia. This assumption comes from the fact that its main biocontrol comes from Pakistan.
Willows in the genus Salix have the tendency to take over floodplanes and wetland areas. There is debate where or not they were introduced but there is no doubt that they can grow very weedy. In areas like the overflow of the Mississippi, like where we are in this episode, its often the only tree growing and thus forms large monocultures.