Amaranthus hybridus |
Amaranthus deflexus |
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green amaranth, green pigweed, hybrid amaranth, slender pigweed, slim amaranth, smooth amaranth, smooth pigweed |
Argentina amaranth, deflexed amaranth, large-fruit amaranth, low amaranth |
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Habit | Plants glabrous or glabrescent, or distal parts of stem and branches slightly pubescent when young. | Plants short-lived perennial or annual, pubescent in distal parts of plant or becoming glabrescent at maturity. |
Stems | erect, green or sometimes reddish purple, rarely under-developed plants ascending, branched to nearly simple, 0.3–2(–2.5) m. |
ascending or prostrate, profusely branched basally, radiating from rootstock, mostly 0.2–0.5 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 1/2 as long as to equaling blade; blade rhombic-ovate or ovate to lanceolate, 1–2 × 0.5–1 cm, base tapering or cuneate, margins entire, plane or slightly undulate, apex subacute, obtuse, or retuse or shallowly emarginate, mucronulate. |
Bracts | lanceolate-linear to subulate, 2–3.5(–4) mm, subequal to or 2 times as long as tepals, apex spinescent. |
of pistillate flowers linear, 0.5–1 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. |
terminal, erect, compact, pyramidal panicles and also some axillary clusters, green or silvery green, occasionally tinged with red, leafless at least distally. |
Staminate flowers | at tips of inflorescences; tepals 5; stamens (4–)5. |
clustered at tips of inflorescences; tepals 2–3; 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 2–3, narrowly elliptic or oblanceolate, not clawed, equal or subequal, 1.2–2 mm, apex broadly acute; style branches erect; stigmas 3. |
Seeds | black to dark reddish brown, lenticular to lenticular-globose, 1–1.3 mm, smooth, shiny. |
very dark brown to black, 1–1.2 mm diam., shiny, filling only proximal portion of fruit. |
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. |
marked with 2(–3) green lines that intersect at apex and divide fruit into halves or quarters, slightly to distinctly inflated, ellipsoid, 2–3 mm, distinctly longer than tepals, smooth (in dry plants wrinkled or rugose), indehiscent. |
Amaranthus hybridus |
Amaranthus deflexus |
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Phenology | Flowering summer–fall. | Flowering summer–fall. |
Habitat | Waste places, agricultural and fallow fields, railroads, roadsides, riverbanks, other disturbed habitats | Weedy areas, ballast heaps, railroads, other disturbed habitats |
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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AL; CA; FL; GA; LA; MA; NJ; NY; OR; PA; TN; VA; native to South America [Introduced in North America; locally introduced or naturalized in tropical to warm-temperate regions of the globe]
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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.) |
The hybrid between Amaranthus deflexus and A. muricatus was described from Europe as A. ×tarraconensis Sennen & Pau (see J. L. Carretero 1979) and may be expected in North America in the future in places of possible co-occurrence of the parental species. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 4. | FNA vol. 4, p. 430. |
Parent taxa | Amaranthaceae > Amaranthus > subg. Amaranthus | Amaranthaceae > Amaranthus > subg. Albersia |
Sibling taxa | ||
Name authority | Linnaeus: Sp. Pl. 2: 990. (1753) | Linnaeus: Mant. Pl. 2: 295. (1771) |
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