Potamogeton foliosus is a perennial, submersed monocotyledon, rooted aquatic herb, colonial from rhizomes, stems to 70 cm long, rooting at nodes, very thin, slightly flattened, to 0.1 cm wide, branching.
Leaves alternate, linear, to 10 cm long, 0.25 cm wide, tip pointed, one major vein with a secondary vein on either side, connecting to midrib near tip, connections alternate; leaf base with sheathing, tubular stipule in each leaf axil, delicate, brownish or greenish, 0.5-2 cm long, margins at first fused, becoming free, eventually deciduous; winter buds to 1.8 x 0.2 cm, in axils or ends of branches (uncommon) (Ogden 1974; Sculthorpe 1985).
Flowers tiny, in 1-2 whorls; flower spikes on a stalk to 1 cm long, inflorescence rounded to 0.7 cm.
Fruit a brownish achene, flattened, asymmetric, with a wavy wing on back part of margin, beak off-center; blooming and fruiting July-Sept (Hough 1983). Seeds and plants eaten by many waterfowl and shore birds and by muskrats (Martin et al. 1951).
Wetland status: OBL.
Frequency in NYC: Very infrequent.
Habitat: Brackish or somewhat alkaline water.