Pondweed, a weedy plant found in shallow freshwater. It is sometimes a pest in lily ponds. Anchored by its roots in bottom mud, the pondweed has branching stems with narrow leaves below the surface of the water; and oval, parallel-veined leaves, about one inch (2.5 cm) long, that float on the surface. Spikes of small greenish flowers appear above the water in midsummer. The nutlike fruits are eaten by waterfowl.
Most pondweeds belong to the pondweed family, Potamogetonaceae. Canadian pondweed belongs to the family Hydrocharitaceae