Potamogeton pusillus is a perennial, submerged monocotyledon, rooted aquatic, stems filamentous, to 1.5 m long, branching near ends.
Leaves alternate, all submerged, linear 1-7 cm long, to 0.2 cm wide with 1-3 veins, 2 small, translucent glands at base, sheath at base of leaf to 1 cm long, membranous, free above; winter buds 1-3 cm, leaves rolled into a hard spindle-shaped body in axils along branches.
Flowers tiny, in round to cylindrical spikes 0.2-1 cm long, at ends of stalks 0.5-6 cm long.
Fruit an oval achene 0.2 cm long, minutely beaked (use lens); blooming and fruiting July-Sept (Hough 1983).
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Acid to alkaline water.