Annual 30-150 cm tall, reddish-purple. Stems erect, branched, pubescent to glabrescent, Leaves petiolate, lanceolate to rhombic-ovate, 3-10 x 2-8 cm, Terminal inflorescence spicate to paniculate with many patent branches. Bracteoles lanceolate-acuminate, 2-3 mm. Perianth segments 5, oblong-lanceolate, 1.5-2 mm, acute. Fruit longer than perianth, 2-2.5 mm, splitting transversely. Seed c. 1 mm, black or pale coloured. Fl. 9-11.Fallow fields and terraces, ruderal places, near coastal saltmarshes, sea level to 350 m.
Naturalised escape from cultivation. Unknown in the wild state. Originating in C. America and introduced to Europe from China in the early 18th century.