Plants glabrous or nearly so. Stems erect or ascending, often whitish or tinged with red, simple to sparingly branched distally, or occasionally basally, 0.2–1 m. Leaves: petiole shorter than to ± equaling blade; blade rhombic-ovate to elliptic-lanceolate, 1.5–6 × 0.5–3 cm, base broadly to narrowly cuneate, margins entire, plane to slightly undulate, apex obtuse to subacute, or shallowly emarginate, with terminal mucro. Inflorescences terminal and axillary in distal part of plant, erect, usually reddish green, branched, leafless at least distally, short and thick. Bracts linear-lanceolate to subulate, to 2 times as long as tepals, apex spinescent. Pistillate flowers: tepals 5, spatulate-linear, not clawed, subequal or unequal, 1.5–2 mm, membranaceous, apex emarginate or retuse to obtuse, outer tepals with apex rarely subacute; style branches shorter than body of fruit; stigmas 3. Staminate flowers few at tips of inflorescences; tepals 5; stamens 4–5. Utricles subglobose to broadly obovoid, 1.3–2 mm, equal or subequal to tepals, smooth or slightly rugose, dehiscence regularly circumscissile. Seeds dark reddish brown to nearly black, lenticular to subglobose-lenticular, 1 mm diam., smooth, shiny.
Phenology: Flowering summer–fall.
Habitat: Naturally disturbed habitats, streambanks, canyons, semideserts
Elevation: 500-2000 m
Ariz., Colo., N.Mex., Tex.
Amaranthus wrightii seems to be closely related to A. retroflexus. In some herbaria the specimens of A. acanthochiton J. D. Sauer (previously known as Acanthochiton wrightii Torrey, see above) were mechanically “transferred” to Amaranthus and erroneously placed in folders as “Amaranthus wrightii.” That confusion was caused by the identical species epithets; these two taxa are dramatically different morphologically. Amaranthus wrightii may also occur in adjacent Mexico.