Amaranthus hybridus
Amaranthus graecizans
green amaranth, green pigweed, hybrid amaranth, slender pigweed, slim amaranth, smooth amaranth, smooth pigweed
Mediterranean amaranth, spreading pigweed, tumbleweed
erect, green or sometimes reddish purple, rarely under-developed plants ascending, branched to nearly simple, 0.3–2(–2.5) m.
erect to ascending or decumbent, branched at or distal to base, 0.1–0.9 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 variable in length;
blade lanceolate to nearly linear or rhombic-ovate to elliptic-ovate, (1.5–)2–4(–5) × 1–3 cm, base cuneate to broadly cuneate, margins entire, plane, rarely indistinctly undulate, apex subacute to obtuse or emarginate, mucronulate.
lanceolate-linear to subulate, 2–3.5(–4) mm, subequal to or 2 times as long as tepals, apex spinescent.
lanceolate, subspinescent, 1.5–2 mm, shorter or slightly longer than tepals.
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 glomerules, green.
at tips of inflorescences;
tepals 5;
stamens (4–)5.
intermixed with pistillate;
tepals 3, equal or subequal;
stamens 3.
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 3, erect, elliptic to lanceolate-elliptic, equal or subequal, 1.5–2 mm, apex short-acuminate;
style branches slightly spreading;
stigmas (2–)3.
black to dark reddish brown, lenticular to lenticular-globose, 1–1.3 mm, smooth, shiny.
black, lenticular, 1–1.3(–1.6) mm diam., smooth or indistinctly punctate.
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 elliptic, 2–2.5 mm, slightly rugose, dehiscence regularly circumscissile, rarely irregularly dehiscent.
Amaranthus hybridus
Amaranthus graecizans
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.)
In North America the name Amaranthus graecizans has been constantly misapplied to the common North American taxa A. albus and A. blitoides. Consequently, A. graecizans has been excluded from lists of North American plants. Recently, herbarium specimens (casual aliens collected in 1879 on ballast in Camden, New Jersey) of A. graecizans subsp. sylvestris were discovered (M. Costea et al. 2001b). Probably, the species disappeared in North America long ago, but, considering the long history of misidentification and confusion, there is also some chance that it may occur locally as an introduced species.
Three subspecies are usually recognized within Amaranthus graecizans in the Old World: subsp. graecizans, subsp. sylvestris (Villars) Brenan, and subsp. thellungianus (Nevski) Gusev. Only subsp. sylvestris, characterized by rhombic-ovate to elliptic-ovate leaves (as compared to lanceolate to almost linear leaves in subsp. graecizans) and comparatively large seeds has so far been reported from North America.
Despite its superficial similarity to Amaranthus albus and A. blitoides, A. graecizans seems to be more closely related to other Old World taxa with trimerous flowers.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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