Stems 10--30 cm. Leaves: stipules persistent; those on proximal portion of stem tightly clasping or slightly enlarged, to 1 mm wide. Inflorescences: peduncles with flower and / or fruits adjacent or separated by less than 2 cm. Fruits common. 2n = 78.

Flowering spring--early fall. Calcareous, saline, or brackish shallow to deep waters of ponds, lakes, streams, ditches, and coastal inshore waters; 0--3280 m; Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Maine, Mich., Minn., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Oreg., Pa., S.Dak., Utah, Vt., Wash., Wis., Wyo.; Asia.

No specimens have been seen from Maryland, but the subspecies is to be expected there.

One hybrid, P. filiformis ´ P. pectinatus (= P. ´ suecicus K. Richter), with this species as a putative parent has been described under the genus Potamogeton.