Amaranthus hybridus |
Amaranthus subg. Amaranthus |
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green amaranth, green pigweed, hybrid amaranth, slender pigweed, slim amaranth, smooth amaranth, smooth pigweed |
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Habit | Plants glabrous or glabrescent, or distal parts of stem and branches slightly pubescent when young. | Plants annual, usually monoecious (in some species, staminate flowers rare). |
Stems | erect, green or sometimes reddish purple, rarely under-developed plants ascending, branched to nearly simple, 0.3–2(–2.5) m. |
usually erect, not fleshy. |
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. |
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Bracts | lanceolate-linear to subulate, 2–3.5(–4) mm, subequal to or 2 times as long as tepals, apex spinescent. |
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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 and axillary, ± long, cylindric spikes or panicles; axillary inflorescences similar to terminal ones, but shorter. |
Staminate flowers | at tips of inflorescences; tepals 5; stamens (4–)5. |
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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. |
tepals usually (3–)5. |
Seeds | black to dark reddish brown, lenticular to lenticular-globose, 1–1.3 mm, smooth, shiny. |
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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. |
transversely dehiscent (except A. bouchonii Thellung and some forms of A. spinosus and A. obcordatus). |
Amaranthus hybridus |
Amaranthus subg. Amaranthus |
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Phenology | Flowering summer–fall. | |
Habitat | Waste places, agricultural and fallow fields, railroads, roadsides, riverbanks, other disturbed habitats | |
Elevation | 0-2500 m (0-8200 ft) | |
Distribution |
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]
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North America; Central America; South America; one species perhaps native to Europe; introduced into other regions |
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.) |
Species ca. 20 (14 in the flora). (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 |
Sibling taxa | ||
Subordinate taxa | ||
Name authority | Linnaeus: Sp. Pl. 2: 990. (1753) | unknown |
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