10. Amaranthus powellii S. Watson ssp. powellii

Pl. 197 h; Map 819

Plants monoecious. Stems 50–200 cm long, erect or ascending, sparsely to moderately pubescent toward the tip with mostly crinkled, multicellular hairs, unarmed. Leaves mostly long-petiolate. Leaf blades 2–12 cm long, lanceolate to ovate or elliptic, narrowed or tapered to a usually bluntly pointed tip (often minutely notched at the very tip), narrowed or tapered at the base, the undersurface sparsely pubescent along the main veins with inconspicuous, mostly crinkled, multicellular hairs. Inflorescences dull or dark green, axillary and terminal, the axillary inflorescences mostly dense globose clusters, the terminal inflorescence a spike or panicle with relatively few, long, ascending branches from near the base, the flowers mostly continuous along the spikes, the tip straight and usually stiffly erect, the main axis and branches often densely pubescent with mostly crinkled, multicellular hairs. Bracts 4–7 mm long, the main body (excluding the awn) conspicuously longer than the sepals and fruits, lanceolate to narrowly oblong-lanceolate or linear-lanceolate, narrowed or tapered to a sharply pointed tip, with a strongly thickened green midrib and relatively narrow, thin, papery margins, the midrib extending beyond the main body as a short awn, spinelike at maturity. Staminate flowers with 3–5 more or less similar sepals, these 1.5–3.0 mm long, erect or ascending, lanceolate to narrowly oblong-lanceolate, narrowed or tapered to a sharply pointed tip, often tapered to a short, awnlike extension of the midrib. Stamens 3(–5). Pistillate flowers with 3–5 more or less similar sepals, these 2–4 mm long, erect, lanceolate to narrowly oblong-lanceolate, narrowed or tapered to a stiff, sharply pointed tip, often tapered to a short, awnlike extension of the midrib. Stigmas 3, spreading from a short, thickened base. Fruits 1.8–2.2 mm long, with circumscissile dehiscence, the surface somewhat roughened or finely wrinkled above the midpoint when dry. Seeds 1.0–1.3 mm in diameter, rounded along the rim, the surface reddish brown to black. 2n=34. June–October.

Introduced, uncommon in eastern and southwestern Missouri (native of western U.S. east to South Dakota and Texas; Canada, Mexico, South America; introduced widely eastward in North America to the East Coast, also Europe). Roadsides, railroads, and open, disturbed areas.