Amaranthus muricatus
Amaranthus acanthochiton
African amaranth, muricate amaranth
greenstripe, greenstripe amaranth
ascending or prostrate, much-branched from stout rootstock, 0.1–0.4 m. Leaves: petiole to 1/2 as long as blade;
blade linear to narrowly lanceolate, 1.5–8 × 0.2–0.5(–1) mm, base tapering, margins entire, plane to undulate, apex obtuse and often emarginate.
erect, much-branched, 0.1–0.8 m;
proximal branches ascending.
petiole shorter than blade;
blade narrowly linear-lanceolate to linear, 2–8 × 0.2–1.2(–1.7) cm, base narrowly cuneate to narrowly decurrent, margins erose, crispate, or irregularly undulate, apex acute to subobtuse.
of pistillate flowers linear, 0.7–1.2 mm, 1/2–2/3 as long as tepals.
completely enfolding flower; of pistillate flowers with prominent excurrent midrib, venation distinct, broadly triangular to deltate, 5+ mm, longer than tepals, margins erose, crenate, or denticulate, apex acute or acuminate; of staminate flowers shorter than tepals, apex acute.
terminal, compact pyramidal panicles and axillary glomerules, erect or reflexed, green, leafless at least distally.
terminal spikes, erect, usually stiff.
intermixed with pistillate or at tips of inflorescences;
tepals 5;
stamens 5.
tepals 5, equal or subequal, 2–3 mm, margins erose to denticulate, outer tepals with apex subobtuse to acute-acuminate;
inner tepals with apex distinctly acuminate or mucronulate;
stamens 5.
tepals 5, narrowly oblanceolate, not clawed, equal, 1.5–2 mm, apex obtuse or subacute;
style branches erect;
stigmas 3.
outer tepals rudimentary, less that 1.2 mm;
inner tepals with venation distinct, 3–4(–5) mm, apex acute, with terminal mucro;
style branches spreading;
stigmas 3.
black, lenticular, 1–1.2 mm diam., semiglossy.
dark reddish brown to brown, 1–1.3 mm diam., shiny.
compressed, subglobose, 1.7–2 mm, ± equaling or slightly exceeding tepals, muricate, indehiscent.
light brown, elliptic to obovate-elliptic, 2(–2.5) mm, shorter than outer tepals, slightly rugose to smooth.
Amaranthus muricatus
Amaranthus acanthochiton
The vernacular name “African amaranth” is sometimes used for this species; it is a misnomer; the species is native to South America and naturalized in Africa.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Amaranthus acanthochiton is very different morphologically from other taxa of dioecious amaranths. In its vegetative and floral morphology, it is similar to the monoecious A. fimbriatus, especially in branching habit, narrow linear to linear-lanceolate leaf blade, and broadly spatulate to almost fan-shaped tepals of the pistillate flowers. These species are also similar phytogeographically, occurring within the southwestern part of the United States and neighboring northern Mexico. The “dioecious amaranths” are an artificial and polyphyletic group consisting of at least two (or three) independently evolved lineages roughly corresponding to the sections of subg. Acnida outlined by S. L. Mosyakin and K. R. Robertson (1996).
Amaranthus acanthochiton is critically imperiled in Utah and imperiled in Arizona; its Global Heritage Status Rank is G5 as defined by The Nature Conservancy. Seeds and young leaves of A. acanthochiton were used by Native Americans (Hopi) as food: the seeds cooked as a kind of porridge, and the leaves cooked and eaten as greens or with meat (D. E. Moerman 1998).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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