Sp. Pl. 2: 1054. 1753.
Herbs, monoecious or subdioecious, 2.5–7.5 (–10) dm. Stems erect or forming sprawling tangled clumps and mostly green; branches erect-ascending, proximal ones opposite and ascending, sparsely scurfy when young, obtusely angled. Leaves alternate or only proximalmost opposite, all shortly petiolate; blade green on both surfaces, linear, linear-oblong, linear-lanceolate, or oblong, (10–) 25–80 (–120) × 2–8 (–12) mm, thin, gradually narrowed, margin mostly entire or some sinuate-dentate with antrorse teeth, apex obtuse to acuminate. Inflorescences of long, dense or interrupted hairy spikes often forming panicle to 20 cm; staminate flowers 4–5-merous. Pistillate bracteoles sessile, triangular to ovate or ovate-rhombic, (3–) 5–7 mm, mostly denticulate, rarely subentire, faces tuberculate almost distinct, green becoming brown or black. Seeds dimorphic: brown, 2–2.8 mm wide, round and ± flattened, or black, 1.5–2 mm wide, round, evenly convex; radicle inferior. 2n = 18.
Phenology: Flowering summer.
Habitat: Sea beaches and other saline habitats, old ports and ballast dumps
Elevation: mainly below 100 m
Introduced; N.B., N.S., P.E.I., Ill., Ind., Maine, Mass., Mich., N.H., Ohio, Pa., Europe