Plant bodies 1.5–2 times as long as wide; 3–5(7) veins; lower surface smooth and reddish purple; upper surface green with papillae along the midline.
Roots up to 7 cm long.
Ponds, lakes, slow moving or stagnant water. 0–100 m. ECas, Est, Sisk, WV. CA, WA; throughout southern North America; temperate to subtropical regions worldwide. Exotic.
This species was first collected in Oregon in 1993, with several more recent, scattered collections at low elevations west of the Cascades. Brown pigment cells in the epidermis, visible in dead plants, give a punctate, or dotted, appearance.
as described under Spirodela punctata
Roots (1--)2--7(--12), to 7 cm, all perforating scale. Fronds obovate, flat or gibbous, 1.5--8 mm, 1.5--2 times as long as wide, apex mostly pointed, upper surface without red spot; veins (3--)5--7; distinct turions absent. Flowers: ovaries 1--2-ovulate. Fruits 0.8--1 mm, laterally winged to apex. Seeds with 10--15 distinct ribs. 2n = 40, 46, 50...Flowering (rare) summer-early fall. Eutrophic, quiet waters, in warm-temperate to subtropical regions with mild winters; 0--900 m; introduced; Ala., Ariz., Ark., Calif., D.C., Fla., Ga., Ill., Ky., La., Miss., Mo., N.C., Okla., Oreg., Pa., S.C., Tenn., Tex., Va., Wash.; South America; Asia; Africa; Atlantic Islands; Pacific Islands; Australia.