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green amaranth, green pigweed, hybrid amaranth, slender pigweed, slim amaranth, smooth amaranth, smooth pigweed

greenstripe, greenstripe amaranth

Habit Plants glabrous or glabrescent, or distal parts of stem and branches slightly pubescent when young. Plants glabrous or glabrescent.
Stems

erect, green or sometimes reddish purple, rarely under-developed plants ascending, branched to nearly simple, 0.3–2(–2.5) m.

erect, much-branched, 0.1–0.8 m;

proximal branches ascending.

Leaves

petiole 1/2 as long as to equaling blade;

blade ovate, rhombic-ovate, or lanceolate, (2–)4–15 × (1–)2–6 cm, base cuneate to broadly cuneate, margins entire, apex acute to obtuse, with mucro.

petiole shorter than blade;

blade narrowly linear-lanceolate to linear, 2–8 × 0.2–1.2(–1.7) cm, base narrowly cuneate to narrowly decurrent, margins erose, crispate, or irregularly undulate, apex acute to subobtuse.

Bracts

lanceolate-linear to subulate, 2–3.5(–4) mm, subequal to or 2 times as long as tepals, apex spinescent.

completely enfolding flower; of pistillate flowers with prominent excurrent midrib, venation distinct, broadly triangular to deltate, 5+ mm, longer than tepals, margins erose, crenate, or denticulate, apex acute or acuminate; of staminate flowers shorter than tepals, apex acute.

Inflorescences

terminal and axillary, erect or reflexed, occasionally nodding, green or olive green, occasionally with silvery or reddish purple tint, leafless at least distally, terrminal inflorescence often slightly nodding with numerous shorter branches at base.

terminal spikes, erect, usually stiff.

Staminate flowers

at tips of inflorescences;

tepals 5;

stamens (4–)5.

tepals 5, equal or subequal, 2–3 mm, margins erose to denticulate, outer tepals with apex subobtuse to acute-acuminate;

inner tepals with apex distinctly acuminate or mucronulate;

stamens 5.

Pistillate flowers

tepals 5, lanceolate to lanceolate-linear, subequal or unequal, 1.5–3 mm, membranaceous, apex acute or acuminate, gradually narrowing into aristate tip;

style branches erect, shorter than body of fruit;

stigmas 3.

outer tepals rudimentary, less that 1.2 mm;

inner tepals with venation distinct, 3–4(–5) mm, apex acute, with terminal mucro;

style branches spreading;

stigmas 3.

Seeds

black to dark reddish brown, lenticular to lenticular-globose, 1–1.3 mm, smooth, shiny.

dark reddish brown to brown, 1–1.3 mm diam., shiny.

Utricles

obovoid or elongate-ovoid, 1.5–2.5 mm, shorter than tepals, smooth proximally, lid verrucose or rugose, dehiscence regularly circumscissile, or rarely in some presumably hybrid forms, irregularly dehiscent or indehiscent.

light brown, elliptic to obovate-elliptic, 2(–2.5) mm, shorter than outer tepals, slightly rugose to smooth.

Amaranthus hybridus

Amaranthus acanthochiton

Phenology Flowering summer–fall. Flowering summer–fall.
Habitat Waste places, agricultural and fallow fields, railroads, roadsides, riverbanks, other disturbed habitats Sandy areas, sand dunes, riverbanks, disturbed habitats
Elevation 0-2500 m (0-8200 ft) 1000-2000 m (3300-6600 ft)
Distribution
from FNA
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; PA; RI; SC; SD; TN; TX; VA; VT; WA; WI; WV; BC; MB; NS; ON; QC; Mexico; Central America; South America; West Indies [Widely introduced or naturalized in tropical, subtropical, and warm-temperate regions worldwide]
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; NM; TX; UT; n Mexico (Chihuahua)
[WildflowerSearch map]
[BONAP county map]
Discussion

Originally a riverside pioneer in eastern North America, now Amaranthus hybridus is extremely abundant in agricultural fields and other disturbed habitats. Related cultivated species have been reported from the flora area, including A. caudatus, A. hypochondriacus, and A. cruentus; there is no evidence that they are established; specimens identified as these species are often variants of A. hybridus.

Distribution of Amaranthus hybridus in North America needs clarification because the name was misapplied to other species, notably A. powellii, and specimens of A. retroflexus, A. powellii, and A. hybridus are frequently interchangeably misidentified. Forms of A. hybridus and A. powellii with reddish inflorescences are often misidentified as escaped and hence presumably naturalized, cultivated species A. caudatus Linnaeus, A. hypochondriacus Linnaeus, and A. cruentus Linnaeus.

Amaranthus hybridus is extremely variable. In particular, there are numerous North American specimens with subobtuse tepals and thick inflorescences, suggesting hybridization with A. retroflexus. In Europe such presumably hybrid forms are known as A. ×ozanonii Thellung (A. Thellung 1914–1919).

A new, presumably hybridogenous taxon, Amaranthus ×tucsonensis Henrickson, was recently described from Arizona (J. Henrickson 1999). It was suggested that one of its parents is A. hybridus; the other parental species (probably a species with obtuse or spatulate tepals) remains unknown. The problem of proper taxonomic position and origin of A. ×tucsonensis needs further study.

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

Amaranthus acanthochiton is very different morphologically from other taxa of dioecious amaranths. In its vegetative and floral morphology, it is similar to the monoecious A. fimbriatus, especially in branching habit, narrow linear to linear-lanceolate leaf blade, and broadly spatulate to almost fan-shaped tepals of the pistillate flowers. These species are also similar phytogeographically, occurring within the southwestern part of the United States and neighboring northern Mexico. The “dioecious amaranths” are an artificial and polyphyletic group consisting of at least two (or three) independently evolved lineages roughly corresponding to the sections of subg. Acnida outlined by S. L. Mosyakin and K. R. Robertson (1996).

Amaranthus acanthochiton is critically imperiled in Utah and imperiled in Arizona; its Global Heritage Status Rank is G5 as defined by The Nature Conservancy. Seeds and young leaves of A. acanthochiton were used by Native Americans (Hopi) as food: the seeds cooked as a kind of porridge, and the leaves cooked and eaten as greens or with meat (D. E. Moerman 1998).

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

Source FNA vol. 4. FNA vol. 4, p. 420.
Parent taxa Amaranthaceae > Amaranthus > subg. Amaranthus Amaranthaceae > Amaranthus > subg. Acnida > sect. Acanthochiton
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. hypochondriacus, A. muricatus, 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. 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. 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
Synonyms Acanthochiton wrightii
Name authority Linnaeus: Sp. Pl. 2: 990. (1753) J. D. Sauer: Madroño 13: 44. (1955)
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