Potamogeton pectinatus C. Linnaeus, Sp. Pl. 1: 127. 1753. (as pectinatum)

Rhizomes present; cauline stems terete to slightly compressed, without dark spots, to 75 cm long. Turions absent. Nodal glands absent. Leaves submersed, alternate, more or less spiraling. Submersed leaves sessile; ligules conspicuous, adnate to blade, light green to dark green, not fibrous, not shredding apically, persistent, convolute, 0.8–1.1 cm long, adnate nearly entire length, the apex acute; light green to dark green, linear, not arcuate, 0.4–5.1(–8.5) cm long, 0.2–1 mm wide, with 1 veins, without lacunae each side of midrib, the base parallel–sided, not clasping, without basal lobes, the margins entire, the apex acute to apiculate, without a bristle tip, not cucullate. Inflorescences unbranched, distal only; distal peduncles cylindrical, flexibile, axillary to terminal, erect to ascending, 4.5–11.4 cm long; spikes lying at surface of water, cylindrical to moniliform, 14–31 mm long, the nodes 4–7, internodes 2.5–9.5 mm long. Flowers whorled; perianth spathulate, clawed, the claw 0.5–0.7 mm long, blade 1–1.5 mm long, 1–1.5 mm wide; anthers 1–1.2 mm long; carpels 4. Fruiting gynophore absent. Fruits oblanceolate, brown, turgid, abaxially rounded, laterally rounded, 3.8–4 mm long, 2.5–3.1 mm wide; beak erect to apically recurved, 0.5–1.1 mm long; tubercules absent; embryo less than one full spiral. 2n= 78.

Flowering summer--autumn. Brackish to alkaline waters of lakes, streams, rivers, and estuaries; 0--2400 m; St. Pierre; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon, Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Fla., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; Central America; South America; Eurasia; Australia.

The sago-pondweed is among the most important species as food for waterfowl (Moore 1913). The species reproduces vegetatively by underground tubers, and various duck species, especially canvas backs. Moore (1913) notes that in a study of the food for ducks, a population of canvas backs was observed feeding in aquatic vegetation composed of several genera, as well as the sago-pondweed. When sacrificed and the stomach contents examined, the ducks had essentially 100% stomach content of tubers of sago-pondweed.

Two hybrids with this species as a putative parent have been described under the genus Potamogeton. These are P. pectinatus ´ P. vaginatus = P. ´ bottnicus J. O. Hagström and P. filiformis ´ P. pectinatus = P. ´ suecicus K. Richter.