Potamogeton foliosus subsp. foliosus
Stems: glands rarely present, less than or equal to 0.3 mm diam. Leaves: stipules greenish to brown, delicate to slightly fibrous, veins decaying with age. Inflorescences: spikes continuous, rarely interrupted. Fruits olive-green to green-brown, 1.5–2.7 × 1.2–2.2 mm; keel greater than or equal to 0.2 mm high; beak 0.2–0.6 mm. 2n = 28.
Phenology: Flowering and fruiting spring–fall.
Habitat: Wide variety of waters of lakes and streams, either slow- or rapidly flowing
Elevation: 0–2300 m
Alta., B.C., Man., N.B., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon, Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo., Mexico, West Indies, Central America (Guatemala, Costa Rica).
Potamogeton foliosus subsp. foliosus is probably the most common linear-leaved species of the family in North America, and it is probably the easiest to determine. Any linear-leaved Potamogeton specimen with fruits having an undulating winglike abaxial keel most likely is this taxon.