An erect sparingly pilose to evenly pubescent annual herb commonly up to 60 cm, sometimes taller. Leaves sessile. Stem-leaves and pseudumbel-leaves broadly ovate to elliptic-ovate, up to 6 x 4 cm, abruptly acutely acuminate or obtuse to subacute and mucronate at the apex, rounded or cuneate at the base, entire, green. Pseudumbel 3-rayed. Ray-leaves elliptic-lanceolate, -oblong or -oblanceolate, the lower 4 x 2 cm, becoming progressively smaller upwards, with white margins, narrow on the lower leaves, becoming progressively broader in the upper ones. Stipules fugacious. Cyathia axillary, or pseudodichasially arranged. Glands transversely ovate, ochreous, with white suborbicular appendages 2-3.5 mm across. Fruits roundly trilobate, 4.5 x 7mm, smooth, sparingly puberulous, pale green, borne on pedicels extending to up to 1.5 cm. Seeds ovoid-subglobose, 3.5 x 3 mm, muricate and foveolate-reticulate, pale grey or whitish, ecarunculate.

Fl. Aug.; Fr. Oct.

Holotype: USA, Montana, Yellowstone River, July, Lewis s.n. (PH).

Distribution: Native of N. America, but cultivated and escaping in various parts of the Old World. On sandy clay soil. 1000'/305 m. - 5000'/1525 m.