Amaranthus palmeri
Amaranthus acanthochiton
carelessweed, Palmer's amara nth, Palmer's pigweed
greenstripe, greenstripe amaranth
erect, branched, usually (0.3–)0.5–1.5(–3) m;
proximal branches often ascending.
erect, much-branched, 0.1–0.8 m;
proximal branches ascending.
long-petiolate;
blade obovate or rhombic-obovate to elliptic proximally, sometimes lanceolate distally, 1.5–7 × 1–3.5 cm, base broadly to narrowly cuneate, margins entire, plane, apex subobtuse to acute, usually with terminal mucro.
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 with long-excurrent midrib, 4–6 mm, longer than tepals, apex acuminate or mucronulate; of staminate flowers, 4 mm, equaling or longer than outer tepals, apex long-acuminate.
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, linear spikes to panicles, usually drooping, occasionally erect, especially when young, with few axillary clusters, uninterrupted or interrupted in proximal part of plant.
terminal spikes, erect, usually stiff.
tepals 5, unequal, 2–4 mm, apex acute;
inner tepals with prominent midrib excurrent as rigid spine, apex long-acuminate or mucronulate;
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 1.7–3.8 mm, apex acuminate, mucronulate;
style branches spreading;
stigmas 2(–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.
dark reddish brown to brown, 1–1.2 mm diam., shiny.
dark reddish brown to brown, 1–1.3 mm diam., shiny.
tan to brown, occasionally reddish brown, obovoid to subglobose, 1.5–2 mm, shorter than tepals, at maturity walls thin, almost smooth or indistinctly rugose.
light brown, elliptic to obovate-elliptic, 2(–2.5) mm, shorter than outer tepals, slightly rugose to smooth.
Amaranthus palmeri
Amaranthus acanthochiton
Originally native to the North American Southwest, from southern California to Texas and northern Mexico, Amaranthus palmeri at present is a successful invasive species, which is evident from its expansion both in eastern North America and overseas. Because of its rapid spread, the distribution data presented here are probably incomplete.
(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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