6. Amaranthus watsonii Standley, Bull. Torrey Bot. Club. 41: 505. 1914 (as watsoni).
Plants pubescent and glandular-pubescent, especially on bracts. Stems ascending to erect, usually much-branched, 0.1-1 m; branches usually ascending. Leaves: petiole shorter than or equaling blade; blade ovate, obovate to elliptic, or oblong-elliptic, 1-8 × 0.5-4 cm, base broadly cuneate to nearly rounded, margins entire, plane or slightly undulate, apex obtuse to emarginate, usually with terminal mucro. Inflorescences mostly terminal, erect spikes to panicles, usually thick and uninterrupted, with few axillary clusters in basal part of plant. Bracts: of pistillate flowers with long-excurrent midrib, 3-4 mm, longer than tepals, apex long-acuminate or mucronulate; of staminate flowers 2.5-4 mm, usually equaling outer tepals, apex long-acuminate or mucronulate. Pistillate flowers: tepals with dark midribs not excurrent, spatulate to fan-shaped, 1.7-2.2 mm, apex obtuse, with terminal mucro; style branches spreading; stigmas 2(-3). Staminate flowers: tepals 5, equal or subequal, 1.5-2(-3) mm, apex acute or almost obtuse; inner tepal apex acuminate or mucronulate; stamens 3-5. Utricles light brown to brown, obovoid to subglobose, 1.5-2 mm, shorter than tepals, walls thin, smooth or indistinctly rugose. Seeds dark reddish brown to nearly black, (0.8-)1-1.2 mm diam., shiny.
Flowering late winter-spring, summer-fall. Coastal dunes, beaches, sandy inland areas, weakly saline flats; 0-100 m; Ariz., Calif.; Mexico (Baja California, Baja California Sur, Sonora); Europe (reported as rare, non-naturalized casual alien).