Rhizomes present; cauline stems terete, without dark spots, to 100 cm long. Turions absent. Nodal glands absent. Leaves submersed and floating, although either type may be absent on certain individuals, alternate, more or less spiraling. Submersed leaves petiolate; ligules conspicuous, free from blade, light brown, not fibrous, not shredding apically, persistent, convolute, 3–9 cm long, the apex obtuse to acute; petiole compressed, 2–13 cm; leaf blade lax, light green to dark green, acicular to lanceolate, not arcuate, 9–20 cm long, 1–3.5 mm wide, with 7–15 veins, 2–5 rows of lacunae each side of midrib, the base cuneate, not clasping, without basal lobes, the margins entire, the apex aristate, not cucullate. Floating leaves petiolate; petiole continuous in color to apex, terete, 3.5–26 cm long; leaf blade adaxially light green, ovate to oblong or obovate, 3–11 cm long, 15–45 mm wide, the veins 9–21, base oblique to obtuse, apex acute or mucronulate or obtuse, without terminal bristle. Inflorescences unbranched, distal only; distal peduncles cylindrical, turgid, axillary or terminal, erect to ascending, 3–15 cm long; spikes emersed, cylindrical, 20–70 mm long, the nodes 6–14, internodes 2–5 mm long. Flowers whorled; perianth spathulate, clawed, the claw 0.8–1.5 mm long, the blade 1.5–2.2 mm long, 2.6–3.1 mm wide; anthers 0.5–1.1 mm long; carpels 4. Fruiting gynophore absent. Fruits obovate, red brown to red, turgid, abaxially angled, laterally angled, 2.7–4.3 mm long, 2.5–3 mm wide; abaxial angles keeled; lateral angles keeled, with blunt to sharp points; beak erect, 0.2–0.3 mm long; tubercules absent; embryo ca. one full spiral. 2n= 52.

Flowering summer--fall. Clear to turbid waters of lakes, streams, rivers, and sloughs; 5--2750 m; Alta., B.C., Ont., Que.; Sask., Ala., 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, South America; Eurasia.

Six hybrids, Potamogeton gramineus ´ P. nodosus = P. ´ argutulus J. O. Hagström, P. illinoensis ´ P. nodosus = P. ´ faxonii T. Morong, P. nodosus ´ P. richardsonii = P. ´ rectifolius A. Bennett, P. natans ´ P. nodosus = P. ´ schreberi F. E. L. Fischer (P. ´ perplexus A. Bennett), P. alpinus ´ P. nodosus = P. ´ subotusus J. O. Hagström, and P. epihydrus ´ P. nodosus = P. ´ subsessilis J. O. Hagström, have been described.

Potamogeton nodosus is a common floating-leaved species throughout much of the United States and southern Canada. When both submersed and floating leaves are present, this is a very easily recognized species by the petioles of the submersed leaves being greater than 5 cm long.