Erect annual, 15-100 cm. Stem shortly and densely hairy. Leaves 3-7 x 2-4 mm, rhomboid-ovate, ± tapered at both ends, somewhat undulate, glabrous. Inflorescence of dense-flowered, ± ebracteate pseudo-spikes, the terminal spike not much longer than the laterals. Bracteoles hard and sharp-pointed, 3-6 mm. Perianth of the female flowers with 5 linear-cuneate to spathulate, usually retuse, shortly mucronulate segments. Fruit with a wrinkled lid. Fl. 5-7. Roadsides, waste places and on cultivated land, s.I.-1900 m.
N. America; introduced throughout the world.