Amaranthus deflexus |
Amaranthus tuberculatus |
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Argentina amaranth, deflexed amaranth, large-fruit amaranth, low amaranth |
common waterhemp, rough-fruit amaranth, rough-fruit water-hemp, tall water-hemp |
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Habit | Plants short-lived perennial or annual, pubescent in distal parts of plant or becoming glabrescent at maturity. | |
Stems | ascending or prostrate, profusely branched basally, radiating from rootstock, mostly 0.2–0.5 m. |
erect to sometimes ascending or rarely prostrate, branched, rarely simple, usually (0.5–)1–2(–3) m. |
Leaves | petiole 1/2 as long as to equaling blade; blade rhombic-ovate or ovate to lanceolate, 1–2 × 0.5–1 cm, base tapering or cuneate, margins entire, plane or slightly undulate, apex subacute, obtuse, or retuse or shallowly emarginate, mucronulate. |
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 | of pistillate flowers linear, 0.5–1 mm, 1/2 as long as tepals. |
of pistillate flowers 1–2 mm; of staminate flowers with inconspicuous to prominent midrib, 1–2 mm, apex acuminate to short-subulate. |
Inflorescences | terminal, erect, compact, pyramidal panicles and also some axillary clusters, green or silvery green, occasionally tinged with red, leafless at least distally. |
terminal, linear spikes to panicles, occasionally interrupted-moniliform, remote, globose glomerules. |
Staminate flowers | clustered at tips of inflorescences; tepals 2–3; stamens 2–3. |
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 2–3, narrowly elliptic or oblanceolate, not clawed, equal or subequal, 1.2–2 mm, apex broadly acute; style branches erect; stigmas 3. |
tepals absent or 1–2, often rudimentary, 1–3 mm; style branches ± erect; stigmas 3. |
Seeds | very dark brown to black, 1–1.2 mm diam., shiny, filling only proximal portion of fruit. |
dark reddish brown to dark brown, 0.7–1 mm diam., shiny. |
Utricles | marked with 2(–3) green lines that intersect at apex and divide fruit into halves or quarters, slightly to distinctly inflated, ellipsoid, 2–3 mm, distinctly longer than tepals, smooth (in dry plants wrinkled or rugose), indehiscent. |
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 deflexus |
Amaranthus tuberculatus |
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Phenology | Flowering summer–fall. | Flowering summer–fall. |
Habitat | Weedy areas, ballast heaps, railroads, other disturbed habitats | Wet areas, such as margins of rivers, ponds, marshes, lakes, and creeks, disturbed habitats, such as agricultural fields, roadsides, and railroads |
Elevation | 0-500 m [0-1600 ft] | 0-1000 m [0-3300 ft] |
Distribution |
AL; CA; FL; GA; LA; MA; NJ; NY; OR; PA; TN; VA; native to South America [Introduced in North America; locally introduced or naturalized in tropical to warm-temperate regions of the globe]
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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 | The hybrid between Amaranthus deflexus and A. muricatus was described from Europe as A. ×tarraconensis Sennen & Pau (see J. L. Carretero 1979) and may be expected in North America in the future in places of possible co-occurrence of the parental species. (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, p. 430. | FNA vol. 4. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | 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: Mant. Pl. 2: 295. (1771) | (Moquin-Tandon) J. D. Sauer: Madroño 13: 18. (1955) |
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