Amaranthus hybridus |
Amaranthus polygonoides |
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green amaranth, green pigweed, hybrid amaranth, slender pigweed, slim amaranth, smooth amaranth, smooth pigweed |
smartweed amaranth, tropical amaranth |
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Habit | Plants glabrous or glabrescent, or distal parts of stem and branches slightly pubescent when young. | Plants annual, glabrescent proximally, pubescent distally, becoming glabrous at maturity. |
Stems | erect, green or sometimes reddish purple, rarely under-developed plants ascending, branched to nearly simple, 0.3–2(–2.5) m. |
erect-ascending to prostrate, branched mostly at base and in proximal 1/2, 0.1–0.5 m. |
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 ± equaling blade; blade ovate, obovate-rhombic to narrowly ovate, sometimes lanceolate, 1.5–3(–4) × 0.5–1.5(–2) cm, base cuneate, margins entire to undulate-erose, apex rounded, obtuse, or emarginate, mucronate. |
Bracts | lanceolate-linear to subulate, 2–3.5(–4) mm, subequal to or 2 times as long as tepals, apex spinescent. |
of pistillate flowers lanceolate or linear, 1–1.5 mm, 1/2 as long as tepals. |
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. |
axillary, congested clusters. |
Staminate flowers | at tips of inflorescences; tepals 5; stamens (4–)5. |
intermixed with pistillate; tepals (4–)5; stamens 2–3. |
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 5, connate in proximal 1/3 (entirely distinct in all other species), with 3 prominent veins abaxially, spatulate or somewhat clawed, equal or subequal, 2–3 mm, apex rounded or retuse, mucronate; style branches somewhat spreading; stigmas 3. |
Seeds | black to dark reddish brown, lenticular to lenticular-globose, 1–1.3 mm, smooth, shiny. |
dark reddish brown to black, lenticular, 0.8–1 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. |
cylindric or narrowly turbinate, 2–2.5 mm, ± equaling tepals, smooth proximally or roughened toward tips, indehiscent or tardily dehiscent. |
Amaranthus hybridus |
Amaranthus polygonoides |
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Phenology | Flowering summer–fall. | Flowering summer–fall. |
Habitat | Waste places, agricultural and fallow fields, railroads, roadsides, riverbanks, other disturbed habitats | Disturbed habitats, coastal areas, near wool-combing mills |
Elevation | 0-2500 m (0-8200 ft) | 0-500 m (0-1600 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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FL; SC; TX; Mexico; West Indies; n South America [Rarely introduced in Europe and some 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.) |
Amaranthus berlandieri often has been recognized as a separate species related to A. polygonoides. J. Henrickson (1999) clarified the confusion that existed in earlier descriptions of these two taxa and showed that the main characters used for their separation (dehiscent versus indehiscent utricles, leaf shape, etc.) are inconsistent and cannot be applied for segregation of two independent species. The subspecies rank may be more appropriate for A. berlandieri, as was suggested by A. Thellung (1914–1919). The relationships between these taxa of the A. polygoniodes aggregate require additional study; in the present treatment we follow the solution proposed by Henrickson. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 4. | FNA vol. 4, p. 432. |
Parent taxa | Amaranthaceae > Amaranthus > subg. Amaranthus | Amaranthaceae > Amaranthus > subg. Albersia |
Sibling taxa | ||
Synonyms | A. berlandieri | |
Name authority | Linnaeus: Sp. Pl. 2: 990. (1753) | Linnaeus: Pl. Jamaic. Pug., 27. (1759) |
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