Plants annual, glabrous. Stems prostrate to ascending (often forming mats), red, much-branched, 0.1-0.4(-0.5) m, fleshy. Leaves clustered near tips of branches; petiole 5-10 mm; blade orbiculate, broadly ovate or obovate, 1-1.5 cm × 1-1.5 cm, fleshy, base broadly cuneate to tapering, margin entire, plane or slightly undulate, apex broadly rounded to obtuse, mucronate. Inflorescences dense axillary glomerules, green. Bracts of pistillate flowers ovate or elliptic, 1.2-2 mm, 1/2 as long as tepals. Pistillate flowers: tepals 5, linear to narrowly oblanceolate, slightly unequal, 2.5-4 mm, margins entire, apex obtuse; style branches erect; stigmas 3. Staminate flowers intermixed with pistillate; tepals 5; stamens 5. Utricles ovoid, 4-6 mm, exceeding tepals, fleshy, smooth or slightly rugose, longitudinally wrinkled on drying, indehiscent. Seeds dark reddish brown, lenticular, 2.5 mm diam., glossy. Flowering summer-fall. Maritime sand dunes, beaches, mostly on foredunes and at high tide level; of conservation concern; 0-10 m; Conn., Del., Md., Mass., N.J., N.Y., N.C., Pa., R.I., S.C., Va. Amaranthus pumilus is in the Center for Plant Conservation´s National Collection of Endangered Plants.
Monoecious; stems fleshy, prostrate or decumbent, branched from the base, 1-4 dm; lvs fleshy, round-obovate, 1-2 cm, ±retuse at the broadly rounded summit, abruptly narrowed to a 5-10 mm petiole; fls in dense axillary clusters; stamens 5; sep of pistillate fls 5, oblong- oblanceolate, unequal, cucullate, 2-4 mm, twice as long as the lanceolate bracts; fr fleshy, indehiscent, thick-fusiform, 4-5 mm, smooth or rugulose; seed elliptic, 2-2.5 mm. Sea-beaches; Mass. to N.C.; rare.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.