Fronds nearly globular, 0.5–1.4 mm (x 0.4–1.2 mm), 1–1.3 times as long as wide, 1–1.3 times as deep as wide, rounded at apex, papilla absent; upper surface transparently green, with 1–10(–30) stomates; pigment cells absent in vegetative tissue. 2n = 30 (H, U), 40 (U), 42 (D), 500 (U), 70 (70), 80 (U).
Phenology: Flowering (very rare) summer–early fall.
Habitat: Mesotrophic to eutrophic, quiet waters in temperate to subtropical regions
Elevation: 0–1100 m
Alta., Man., Ont., Que., Sask., Ala., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis., Mexico, West Indies (Cura�ao), Central America, South America.
I know of no specimens of Wolffia columbiana from Rhode Island.