Polygonum hirsutum grows in swamps, lake shores, and pond margins. It is occasionally found from the northern and central peninsula, west to the central panhandle of Florida (Wunderlin, 2003). It blooms from spring to fall.
Hairy smartweed is only located in Florida, Georgia, Alabama, Mississippi, North Carolina, and South Carolina (Kartesz, 1999).
For brief control information, see Efficacy of Herbicide Active Ingredients Against Aquatic Weeds by K. Langeland, M. Netherland, and W. Haller.