Amaranthus hybridus
Amaranthus wrightii
green amaranth, green pigweed, hybrid amaranth, slender pigweed, slim amaranth, smooth amaranth, smooth pigweed
Wright's amaranth
erect, green or sometimes reddish purple, rarely under-developed plants ascending, branched to nearly simple, 0.3–2(–2.5) m.
erect or ascending, often whitish or tinged with red, simple to sparingly branched distally, or occasionally basally, 0.2–1 m.
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 to ± equaling blade;
blade rhombic-ovate to elliptic-lanceolate, 1.5–6 × 0.5–3 cm, base broadly to narrowly cuneate, margins entire, plane to slightly undulate, apex obtuse to subacute, or shallowly emarginate, with terminal mucro.
lanceolate-linear to subulate, 2–3.5(–4) mm, subequal to or 2 times as long as tepals, apex spinescent.
linear-lanceolate to subulate, to 2 times as long as tepals, apex spinescent.
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 in distal part of plant, erect, usually reddish green, branched, leafless at least distally, short and thick.
at tips of inflorescences;
tepals 5;
stamens (4–)5.
few at tips of inflorescences;
tepals 5;
stamens 4–5.
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, spatulate-linear, not clawed, subequal or unequal, 1.5–2 mm, membranaceous, apex emarginate or retuse to obtuse, outer tepals with apex rarely subacute;
style branches shorter than body of fruit;
stigmas 3.
black to dark reddish brown, lenticular to lenticular-globose, 1–1.3 mm, smooth, shiny.
dark reddish brown to nearly black, lenticular to subglobose-lenticular, 1 mm diam., smooth, shiny.
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.
subglobose to broadly obovoid, 1.3–2 mm, equal or subequal to tepals, smooth or slightly rugose, dehiscence regularly circumscissile.
Amaranthus hybridus
Amaranthus wrightii
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 wrightii seems to be closely related to A. retroflexus. In some herbaria the specimens of A. acanthochiton J. D. Sauer (previously known as Acanthochiton wrightii Torrey, see above) were mechanically “transferred” to Amaranthus and erroneously placed in folders as “Amaranthus wrightii.” That confusion was caused by the identical species epithets; these two taxa are dramatically different morphologically. Amaranthus wrightii may also occur in adjacent Mexico.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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