Plant bodies submersed unless flowering or fruiting, oblong to lanceolate, (3)6–10(15) mm long, 2–3.5 times longer than wide, apex obtuse, and base narrowed to a stipe, (1)3 veins, with the middle vein more prominent; lower surface flat and thin, green, often reddish; in branching networks of about 10–30 plant bodies connected by persistent green stipes, 2–20 mm long.
Roots up to 2.5 cm long, but often absent.
Turions absent.
Freshwater. 200–2100 m. BR, BW, Casc, ECas, WV. CA, ID, NV, WA; throughout North America; Africa, Australia, Eurasia. Native.
as described under Lemna trisulca
Roots to 2.5 cm (sometimes not developed), tip pointed; sheath not winged. Green stalks 2--20 mm. Fronds submersed (except when flowering or fruiting), 3--50, coherent and very often forming branched chains, narrowly ovate, flat, thin, 3--15 mm (excluding stalk), 2--3.5 times as long as wide, base suddenly narrowed into green stalk, margins denticulate distally; veins (1 or) 3, lateral veins only in proximal part of frond; papillae absent; anthocyanin often present; air spaces shorter than 0.3 mm; turions absent. Flowers: ovaries 1-ovulate, utricular scale with narrow opening at apex. Fruits 0.6--0.9 mm, laterally winged toward apex. Seeds with 12--18 distinct ribs, staying within fruit wall after ripening. 2n = 40, 42, 44, 60, 63, 80.Flowering (rare) late spring--summer. Mesotrophic, quiet waters rich in calcium, in cool-temperate regions; 0--3000 m; Alta., B.C., Man., N.B., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Conn., Idaho, Ill., Ind., Iowa, Kans., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; nearly worldwide, except arctic and antarctic regions and South America; in warm regions only in mountains.The report of Lemna trisulca in Florida is dubious because the climate is too warm. The species may be temporarily introduced there by birds.