Amaranthus spinosus

Linnaeus

Sp. Pl. 2: 991. 1753.

Common names: Spiny amaranth thorny amaranth
WeedyIntroducedIllustrated
Treatment appears in FNA Volume 4. Mentioned on page 405, 410, 412, 420.

Plants glabrous or sparsely pubescent in the distal younger parts of stems and branches. Stems erect or sometimes ascending proximally, much-branched and bushy, rarely nearly simple, 0.3–1 (–2) m; each node with paired, divergent spines (modified bracts) to 1.5 (–2.5) cm. Leaves: petiole ± equaling or longer than blade; blade rhombic-ovate, ovate, or ovatelanceolate, 3–10 (–15) × 1.5–6 cm, base broadly cuneate, margins entire, plane or slightly undulate, apex acute or subobtuse to indistinctly emarginate, mucronulate. Inflorescences simple or compound terminal staminate spikes and axillary subglobose mostly pistillate clusters, erect or with reflexed or nodding tips, usually green to silvery green. Bracts of pistillate flowers lanceolate to ovatelanceolate, shorter than tepals, apex attenuate. Pistillate flowers: tepals 5, obovate-lanceolate or spatulate-lanceolate, equal or subequal, 1.2–2 mm, apex mucronate or short-aristate; styles erect or spreading; stigmas 3. Staminate flowers: often terminal or in proximal glomerules; tepals 5, equal or subequal, 1.7–2.5 mm; stamens 5. Utricles ovoid to subglobose, 1.5–2.5 mm, membranaceous proximally, wrinkled and spongy or inflated distally, irregularly dehiscent or indehiscent. Seeds black, lenticular or subglobose-lenticular, 0.7–1 mm diam., smooth, shiny.


Phenology: Flowering summer–fall.
Habitat: Waste places, fields, roadsides, railroads, barnyards, overgrazed pastures, other disturbed habitats
Elevation: 0-700 m

Distribution

Introduced; Man., Ont., Ala., Ark., Calif., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Minn., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis., Mexico, West Indies, Central America, South America, nearly worldwide

Discussion

Amaranthus spinosus is native to lowlands in tropical America; at present it is a pantropical weed that also occurs in some warm-temperate regions.

Amaranthus spinosus, or its ancestral taxon, probably gave rise to the allopolyploid A. dubius by hybridization with some species of the A. hybridus aggregate (see above). Section Centrusa probably occupies a basal position, at least for the clade of subg. Amaranthus sect. Amaranthus, and probably for some representatives of subg. Acnida as currently outlined. Recent results of sequencing the ITS region (including ITS-1, 5.8S rDNA, and ITS-2) of nuclear ribosomal DNA from 15 species of Amaranthus occurring in China also suggest the basal position of A. spinosus among the studied species (Song B. H. et al. 2000). These results also confirm a profound divergence between subgenera Amaranthus and Albersia; the latter is called “sect. Paucestamen” by the above authors. Data on the electrophoretic variation of seed proteins (R. H. Sammour et al. 1993) are also in accord with the segregation of these two subgenera; in the cited article, these groups are called sect. Amaranthus and sect. Blitopsis.

Selected References

None.

Lower Taxa

None.
... more about "Amaranthus spinosus"
Sergei L. Mosyakin +  and Kenneth R. Robertson +
Linnaeus +
cuneate +
10 cm100 mm <br />0.1 m <br /> (15 cm150 mm <br />0.15 m <br />) +
3 cm30 mm <br />0.03 m <br /> (10 cm100 mm <br />0.1 m <br />) +
ovatelanceolate +, ovate +  and rhombic-ovate +
1.5cm;6cm +
persistent +
lanceolate +  and ovatelanceolate +
Spiny amaranth +  and thorny amaranth +
Man. +, Ont. +, Ala. +, Ark. +, Calif. +, Conn. +, Del. +, D.C. +, Fla. +, Ga. +, Ill. +, Ind. +, Iowa +, Kans. +, Ky. +, La. +, Maine +, Md. +, Mass. +, Minn. +, Miss. +, Mo. +, Nebr. +, N.J. +, N.Y. +, N.C. +, Ohio +, Okla. +, Pa. +, R.I. +, S.C. +, Tenn. +, Tex. +, Vt. +, Va. +, W.Va. +, Wis. +, Mexico +, West Indies +, Central America +, South America +  and nearly worldwide +
0-700 m +
peripheral +
staminate +  and pistillate +
hypogynous +
in proximal glomerules +  and terminal +
minute +  and small +
not +  and dehiscent +
Waste places, fields, roadsides, railroads, barnyards, overgrazed pastures, other disturbed habitats +
compound +  and simple +
reduced +
undulate +, plane +  and entire +
scarious +  and membranaceous +
cylindric +
more or less equaling or longer +
Flowering summer–fall. +
rudimentary +
0.07 cm0.7 mm <br />7.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
subglobose-lenticular +  and lenticular +
Weedy +, Introduced +  and Illustrated +
cylindric +
divergent +  and paired +
simple +  and much-branched +
prostrate +  and decumbent +
ascending +  and erect +
30 cm300 mm <br />0.3 m <br /> (100 cm1,000 mm <br />1 m <br />) +
not fleshy +
slender +
spreading +  and erect +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Acanthochiton +, Acnida +, Albersia +, Amblogyna +, Euxolus +, Mengea +, Sarratia +  and Scleropus +
Amaranthus spinosus +
Amaranthus subg. Amaranthus +
species +
distinct +
spatulate-lanceolate +  and obovate-lanceolate +
subequal +
0.17 cm1.7 mm <br />0.0017 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
indurate +, membranaceous +, chartaceous +  and scarious +
pistillate +  and staminate +
usually green;silvery green +
with reflexed or nodding tips +  and erect +
nodding +  and reflexed +
walled +  and 3(-5)-veined +
indehiscent +  and dehiscent +
inflated +, ovoid +  and subglobose +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
spongy +  and membranaceous +
pubescent +  and glabrous +