Amaranthus cruentus |
Amaranthus tuberculatus |
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blood amaranth, caterpillar amaranth, purple amaranth, red amaranth |
common waterhemp, rough-fruit amaranth, rough-fruit water-hemp, tall water-hemp |
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Habit | Plants almost glabrous or slightly pubescent distally, especially when young. | |
Stems | erect, green or reddish purple, branched distally, mostly in inflorescence, to nearly simple, 0.4–2 m. Leaves: petiole 1/2 as long as to ± equaling blade; blade rhombic-ovate or ovate to broadly lanceolate, 3–15(–20) × 1.5–10(–15) cm, occasionally larger in robust plants, base cuneate to broadly cuneate, margins entire, plane, apex acute or subobtuse to slightly emarginate, with mucro. |
erect to sometimes ascending or rarely prostrate, branched, rarely simple, usually (0.5–)1–2(–3) m. Leaves: petiole 1/4–1/2 length of blade; blade ovate or obovate proximally, oblong or elliptic to narrowly lanceolate distally, 1.5–15 × 0.5–3 cm, base cuneate, margins entire, plane, apex obtuse or rounded to acute. |
Bracts | narrowly spathulate, 2–3 mm, equaling or slightly longer than tepals, apex short-spinescent. |
of pistillate flowers 1–2 mm; of staminate flowers with inconspicuous to prominent midrib, 1–2 mm, apex acuminate to short-subulate. |
Inflorescences | terminal and axillary, erect, reflexed, or nodding, usually dark red, purple, or deep beet-red, less commonly almost green or greenish red, leafless at least distally, large and robust. |
terminal, linear spikes to panicles, occasionally interrupted-moniliform, remote, globose glomerules. |
Staminate flowers | at tips of inflorescences; tepals 5; stamens (4–)5. |
tepals 5, inner tepals with prominent midribs excurrent as rigid spines or not, equal to unequal, 2–3 mm, apex obtuse to acute or acuminate or indistinctly mucronulate; stamens 5. |
Pistillate flowers | tepals 5, oblong to lanceolate, not clawed, equal or subequal, 1.5–3 mm, apex acute; style branches erect or slightly reflexed; stigmas 3. |
tepals absent or 1–2, often rudimentary, 1–3 mm; style branches ± erect; stigmas 3. |
Seeds | usually white or ivory, with reddish or yellowish tint, sometimes dark brown to dark reddish brown, broadly lenticular to elliptic-lenticular, 1.2–1.6 mm diam., smooth or indistinctly punctate. |
dark reddish brown to dark brown, 0.7–1 mm diam., shiny. |
Utricles | obovoid to elongate-obovoid, 2–2.5 mm, smooth or slightly rugose distally, dehiscence regularly circumscissile. |
dark brown to reddish brown, not ribbed, obovoid to subglobose, 1.5–2 mm, thin, almost smooth or irregularly rugose, indehiscent, irregularly dehiscent, or dehiscence regularly circumscissile. |
Amaranthus cruentus |
Amaranthus tuberculatus |
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Phenology | Flowering summer–fall. | Flowering summer–fall. |
Habitat | Near places of cultivation | Wet areas, such as margins of rivers, ponds, marshes, lakes, and creeks, disturbed habitats, such as agricultural fields, roadsides, and railroads |
Elevation | 0-1000 m (0-3300 ft) | |
Distribution |
AZ; CA; CT; IL; IN; KY; MA; MD; ME; MI; NC; NE; NH; NJ; NY; OH; OR; PA; RI; SC; TX; UT; VT; WA; WI; WV; Central America; South America; cultivated widely
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AL; AR; CA; CO; CT; DE; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NM; NV; NY; OH; PA; SC; SD; TN; TX; VT; WA; WI; WV; MB; ON; PE; QC [Introduced in North America; introduced, usually not naturalized, in Europe and other continents]
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Discussion | Amaranthus cruentus is cultivated as ornamental and pseudocereal almost worldwide from tropical to warm-temperate regions. While reported as naturalized in several states, most specimens identified as this species are referable to A. hybridus or other native species. Escaped plants of A. cruentus sometimes occur near places of cultivation (see note under A. caudatus). No attempt has been made to summarize distribution data for such escapes. Amaranthus cruentus originated from A. hybridus (most probably in cultivation in Central America), with which it shares almost all major morphologic characteristics. Inclusion of cultivated forms in A. hybridus in a broad sense is thus rather justified. Cultivated species traditionally have been treated as separate taxa in horticultural and agricultural literature, and we prefer to maintain the current convenient usage of these names. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
J. D. Sauer (1967b, 1972b) separated Amaranthus rudis (A. tamariscinus) as distinct from A. tuberculatus, based primarily on absence of tepals in the pistillate flowers and indehiscent fruits. Recent work by D. B. Pratt and L. G. Clark (2001) showed that those characteristics are not constant and they recognized only one polymorphic species, A. tuberculatus. Long-term observations by K. R. Robertson strongly support the inclusion of A. rudis within A. tuberculatus. Amaranthus rudis probably was originally native to the Great Plains west of the Mississippi, from Texas to Iowa. Amaranthus tuberculatus likely had a more northern range, north of Missouri and Tennessee to the Great Lakes. The emerging evolutionary differentiation between the two related taxa was erased by agriculture and human-induced introduction and invasion. Amaranthus tuberculatus has become a major weed of agricultural fields and other disturbed habitats and is now introduced in parts of North America far outside its original range. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 4. | FNA vol. 4. |
Parent taxa | Amaranthaceae > Amaranthus > subg. Amaranthus | Amaranthaceae > Amaranthus > subg. Acnida > sect. Acnida |
Sibling taxa | ||
Synonyms | A. hybridus subsp. cruentus | Acnida tuberculata, Acnida altissima, Acnida altissima var. prostrata, Acnida altissima var. subnuda, Acnida concatenata, Acnida subnuda, Acnida tamariscina, Acnida tamariscina var. concatenata, Acnida tamariscina var. tuberculata, A. ambigens, A. rudis |
Name authority | Linnaeus: Syst. Nat. ed. 10, 2: 1269. (1759) | (Moquin-Tandon) J. D. Sauer: Madroño 13: 18. (1955) |
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