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African amaranth, muricate amaranth

green amaranth, green pigweed, Powell's amaranth, Powell's smooth amaranth

Habit Plants annual or short-lived perennial, glabrous or slightly pubescent near tips. Plants glabrous or moderately pubescent toward inflorescences, becoming glabrescent at maturity.
Stems

ascending or prostrate, much-branched from stout rootstock, 0.1–0.4 m.

usually erect, green or sometimes reddish purple, branched, mainly in inflorescences, to nearly simple, 0.3–1.5(–2) m, stiff.

Leaves

petiole to 1/2 as long as blade;

blade linear to narrowly lanceolate, 1.5–8 × 0.2–0.5(–1) mm, base tapering, margins entire, plane to undulate, apex obtuse and often emarginate.

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.

Bracts

of pistillate flowers linear, 0.7–1.2 mm, 1/2–2/3 as long as tepals.

lanceolate to linear-subulate, 4–7 mm, 2–3 times as long as tepals, rigid.

Inflorescences

terminal, compact pyramidal panicles and axillary glomerules, erect or reflexed, green, leafless at least distally.

mostly terminal, usually with spikes at distal axils, erect and rigid, green to silvery green, occasionally tinged red, leafless at least distally.

Staminate flowers

intermixed with pistillate or at tips of inflorescences;

tepals 5;

stamens 5.

clustered at tips of inflorescence branches;

tepals 3–5;

stamens 3–5.

Pistillate flowers

tepals 5, narrowly oblanceolate, not clawed, equal, 1.5–2 mm, apex obtuse or subacute;

style branches erect;

stigmas 3.

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.

Seeds

black, lenticular, 1–1.2 mm diam., semiglossy.

black, subglobose to lenticular, 1–1.4 mm diam., smooth, shiny.

Utricles

compressed, subglobose, 1.7–2 mm, ± equaling or slightly exceeding tepals, muricate, indehiscent.

subglobose or compressed-ovoid, 2–3 mm, equaling or shorter than tepals, smooth or lid slightly rugose or minutely verrucose, dehiscence regularly circumscissile.

Amaranthus muricatus

Amaranthus powellii

Phenology Flowering summer–fall. Flowering summer–fall.
Habitat Waste places, on ballast Disturbed habitats, agricultural fields, railroads, roadsides, waste areas, banks of rivers, lakes, and streams
Elevation 0 m (0 ft) 0-2500 m (0-8200 ft)
Distribution
from FNA
AL; s South America (Argentina, Paraguay, Uruguay) [Introduced in North America; introduced in s Europe, s Africa, Australia, and other regions]
[BONAP county map]
from FNA
AR; AZ; CA; CO; CT; FL; ID; IL; IN; KS; KY; LA; MA; ME; MI; MN; MO; MS; MT; NC; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; ON; PE; QC; SK; Mexico [Introduced or naturalized in South America, Eurasia, Australia]
[WildflowerSearch map]
[BONAP county map]
Discussion

The vernacular name “African amaranth” is sometimes used for this species; it is a misnomer; the species is native to South America and naturalized in Africa.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 4, p. 431. FNA vol. 4.
Parent taxa Amaranthaceae > Amaranthus > subg. Albersia Amaranthaceae > Amaranthus > subg. Amaranthus
Sibling taxa
A. acanthochiton, A. albus, A. arenicola, A. australis, A. blitoides, A. blitum, A. californicus, A. cannabinus, A. caudatus, A. crassipes, A. crispus, A. cruentus, A. deflexus, A. dubius, A. fimbriatus, A. floridanus, A. graecizans, A. greggii, A. hybridus, A. hypochondriacus, A. obcordatus, A. palmeri, A. polygonoides, A. powellii, A. pumilus, A. retroflexus, A. scleropoides, A. spinosus, A. tamaulipensis, A. thunbergii, A. torreyi, A. tricolor, A. tuberculatus, A. viridis, A. viscidulus, A. watsonii, A. wrightii
A. acanthochiton, A. albus, A. arenicola, A. australis, A. blitoides, A. blitum, A. californicus, A. cannabinus, A. caudatus, A. crassipes, A. crispus, A. cruentus, A. deflexus, A. dubius, A. fimbriatus, A. floridanus, A. graecizans, A. greggii, A. hybridus, A. hypochondriacus, A. muricatus, A. obcordatus, A. palmeri, A. polygonoides, A. pumilus, A. retroflexus, A. scleropoides, A. spinosus, A. tamaulipensis, A. thunbergii, A. torreyi, A. tricolor, A. tuberculatus, A. viridis, A. viscidulus, A. watsonii, A. wrightii
Synonyms Euxolus muricatus A. bracteosus, A. retroflexus var. powellii
Name authority (Moquin-Tandon) Hieronymus: Pl. Diaph. Fl. Argent., 227. (1882) S. Watson: Proc. Amer. Acad. Arts 10: 347. (1875)
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