Amaranthus powellii S. Wats.

Amaranthus powellii is originally native to southwestern United States and adjacent regions of Mexico; now, it is widely naturalized almost everywhere in temperate regions of North America. The distribution of A. powellii is probably underestimated both in North America and the Old World, and literature references are somewhat confusing, because A. powellii has been commonly confused with A. hybridus.

Forms of Amaranthus powellii with indehiscent or occasionally irregularly dehiscent utricles were described from Europe (southwestern France, the Gironde estuary) as A. bouchonii Thellung. Similar forms occasionally occur in North America. According to J. M. Tucker and J. D. Sauer (1958) and J. D. Sauer (1967b, 1972b), they are mostly "mutant or aberrant forms" of A. powellii, or hybrids of A. powellii and/or A. hybridus with other species. Recent comparative studies of morphology and isozymes of A. bouchonii (P. Wilkin 1992) indicated that that taxon, whatever its origin was, now differs from its presumably parental species and probably deserves recognition, at least as a separate subspecies. It seems that in North America, the situation with indehiscent-fruited forms is much more complicated than in Europe, and multiple entities are involved, including deviate forms of A. powellii and also partly sterile hybrids of dioecious taxa with species belonging to the A. hybridus group. The formal recognition of A. bouchonii in North American material would be premature.

The names Amaranthus hybridus, A. chlorostachys Willdenow, and A. hybridus subsp. chlorostachys (Willdenow) Hejný were occasionally misapplied to A. powellii in North America and Europe.

Plants glabrous or moderately pubescent toward inflorescences, becoming glabrescent at maturity. Stems usually erect, green or sometimes reddish purple, branched, mainly in inflores-cences, to nearly simple, 0.3-1.5(-2) m, stiff. Leaves: petiole mostly equaling or longer than blade; blade rhombic-ovate to broadly lanceolate, 4-8 × 2-3 cm, occasionally larger in robust plants, base cuneate to broadly cuneate, margins entire, apex cuneate to obtuse or indistinctly emarginate, with mucro. Inflorescences mostly terminal, usually with spikes at distal axils, erect and rigid, green to silvery green, occasionally tinged red, leafless at least distally. Bracts lanceolate to linear-subulate, 4-7 mm, 2-3 times as long as tepals, rigid. Pistillate flowers: tepals usually 3-5, not clawed, unequal; outer tepals narrowly ovate-elliptic or elliptic, 1.5-3.5 mm, apex aristate; style branches spreading, shorter than body of fruit; stigmas 3. Staminate flowers clustered at tips of inflorescence branches; tepals 3-5; stamens 3-5. Utricles subglobose or compressed-ovoid, 2-3 mm, equaling or shorter than tepals, smooth or lid slightly rugose or minutely verrucose, dehiscence regularly circumscissile. Seeds black, subglobose to lenticular, 1-1.4 mm diam., smooth, shiny.

Alta., B.C., Ont., P.E.I., Que., Sask.; Ariz., Ark., Calif., Colo., Conn., Fla., Idaho, Ill., Ind., Kans., Ky., La., Maine, Mass., Mich., Minn., Miss., Mo., Mont., Nev., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; introduced or naturalized in South America, Eurasia, Australia.

Flowering summer-fall.

Disturbed habitats, agricultural fields, railroads, roadsides, waste areas, banks of rivers, lakes, and streams; 0-2500m.

Amaranthus bracteosus Uline & W. L. Bray; A. retroflexus Linnaeus var. powellii (S. Watson) B. Boivin

Amaranthus bracteosus Uline & Bray, Bot. Gaz. 19: 314
1894.
Amaranthus viscidulus Greene, Pittonia 3: 344. 1898.
Stems slender or stout, erect or ascending, 1-3 dm. high, much branched from the base or above, whitish, densely viscid-villous, sometimes glabrate in age; petioles slender, 5-25 mm. long; leaf -blades usually shorter than the petioles except in the uppermost leaves, obovate to oblong, oval, rhombic-ovate, or spatulate, 1-4 cm. long, rounded at the apex, sometimes shallowly emarginate, cuneate at the base, thick, yellowishor pale-green, viscid-puberulent or villous on the lower surface, sometimes glabrate in age, nearly glabrous on the upper surface, prominently veined; flowers monoecious, in a stout erect terminal spike 2-10 cm. long and 1-2 cm. thick, and in numerous dense axillary clusters shorter than the petioles; bracts lanceolate, 5-8 mm. long, rigid, spreading, green, with spinose tips, several times as long as the flowers, more or less villous; sepals 5, oblong, obtuse, 1-nerved, the nerve long-excurrent ; stamens 3; style-branches 3, elongate, much thickened at the base; utricle slightly exceeding or equaling the sepals, subglobose or oblong, thick-walled, circumscissile, somewhat rugulose ; seed rotund, 1.2 mm. in diameter, black, shining.
Type locality: New Mexico, probably near Santa Fe. Distribution : Open hillsides, New Mexico.

Amaranthus powellii S. Wats. Proc. Am. Acad. 10: 347. 1875
Amaranthus obovatus S. Wats. Proc. Am. Acad. 12: 275. 1877.
A mar anthus chlorostachys pseudoretroflexus Thellung, Viert. Nat. Ges. Zurich 52: 443. 1907.
Stems stout, 3-20 dm. high, erect, simple, or usually much branched, green or whitish,
glabrous below, usually villous above; petioles slender, 1-5 cm. long; leaf-blades ovate, rhombicovate, rhombic-oval, or rarely lanceolate, 1.5-8 cm. long, 0.5-4 cm. wide, acute to obtuse at the apex, sometimes emargmate, cuneate to acute at the base, yellowish-green or deep-green, glabrous or sparsely pubescent; flowers monoecious, in dense, stout, erect, obtuse, simple or paniculate spikes 4—25 cm. long and 1-2 cm, thick, dense clusters of flowers usually present also in the axils of the upper leaves; bracts 2—3 times' as long as the sepals, lanceolate or ovate, attenuate to a rigid spinose tip, green and indurate along the midnerve, sometimes puberulent; sepals of the staminate flowers lance-oblong, scarious, 1-nerved, acute, the midnerve excurrent; sepals of the pistillate flowers 3 mm. long, oblong or lance-oblong, acute or acutish, thin, somewhat thickened at the base, 1-nerved, the nerve usually excurrent as a spinulose tip, usually longer than the fruit; stamens mostly 3; style-branches 3, elongate, erect; utricle Subglobose, compressed, equaling or shorter than the sepals, rugulose above, dehiscent at the middle; seed obovate or oval, about 1.2 mm. long, black and shining.
Type locality: Arizona.
Distribution : Waste or cultivated ground, Oregon to Wyoming and northern Mexico ; adventive in New England, and in Europe.

Amaranthus powellii is a species of amaranth known by the common names Powell's amaranth and green amaranth.

It is native to the southwestern United States and northern Mexico, but it is common throughout most of the rest of the temperate Americas as a naturalized species. It has also been introduced to other continents, including Australia and Europe.