Amaranthus australis

(A. Gray) J. D. Sauer

Madroño 13: 15. 1955.

Common names: Southern water-hemp southern amaranth
WeedyIllustrated
Basionym: Acnida australis A. Gray Amer. Naturalist 10: 489. 1876
Synonyms: Acnida alabamensis Standley Acnida cannabina var. australis (A. Gray) Uline & W. L. Bray Acnida cuspidata Bertero ex Sprengel
Treatment appears in FNA Volume 4. Treatment on page 416. Mentioned on page 412, 413.

Stems erect, branched, stout to robust, usually 1.5–3 m (occasionally to 9 m!) × 30 cm. Leaves: petiole 1/3–2/3 length of blade; blade narrowly lanceolate to narrowly ovate, 10–20 × 1–4 cm, base cuneate, margins entire, plane, apex acute or long-attenuate to acuminate. Inflorescences mostly terminal, linear spikes to panicles, usually interrupted. Bracts: of pistillate flowers 1.5–2 mm; of staminate flowers with moderately heavy midribs, 1.5–2 mm. Pistillate flowers: tepals absent; style-branches spreading; stigmas 3–5. Staminate flowers: tepals 5, inner tepals with moderately prominent, excurrent midribs, equal, 2–2.5 mm, apex subacute to mucronulate; stamens 5. Utricles stramineous to brown, with 3 (–5) longitudinal ridges corresponding to 3–5 style-branches, elliptic or obovoid, 1.5–2.5 mm, slightly fleshy, smooth (slightly rugose in herbarium specimens). Seeds reddish-brown to dark-brown, 1–1.2 mm diam., shiny.


Phenology: Flowering summer–fall.
Habitat: Freshwater and brackish wetland habitats, coastal marshes, swamps, riverbanks, bayous, canals, ditches, estuaries, lakeshores, hammocks
Elevation: 0-100 m

Distribution

Ala., Ark., Fla., Ga., La., Miss., N.C., Tenn., Tex., Va., e Mexico, West Indies, n South America

Discussion

Plants of Amaranthus australis, a herbaceous annual, can be amazingly tall, with a single hollow main stem, up to 9 m, and the stem base can reach 30 cm in diameter. Large plants may somewhat resemble young trees of Taxodium distichum var. imbricarium, pondcypress.

Selected References

None.

Lower Taxa

None.

"/3lengthofblade" is not declared as a valid unit of measurement for this property. "/3lengthofblade" is not declared as a valid unit of measurement for this property.

... more about "Amaranthus australis"
subacute;mucronulate +
Sergei L. Mosyakin +  and Kenneth R. Robertson +
(A. Gray) J. D. Sauer +
cuneate +
Acnida australis +
10 cm100 mm <br />0.1 m <br /> (20 cm200 mm <br />0.2 m <br />) +
narrowly lanceolate +  and narrowly ovate +
1 cm10 mm <br />0.01 m <br /> (4 cm40 mm <br />0.04 m <br />) +
elliptic to subulate-linear +  and elliptic +
persistent +
triangular +, deltate +, subulate +, linear +, lanceolate +  and ovate +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
Southern water-hemp +  and southern amaranth +
Ala. +, Ark. +, Fla. +, Ga. +, La. +, Miss. +, N.C. +, Tenn. +, Tex. +, Va. +, e Mexico +, West Indies +  and n South America +
0-100 m +
peripheral +
staminate +  and pistillate +
not enfolding +
minute +  and small +
not +  and dehiscent +
Freshwater and brackish wetland habitats, coastal marshes, swamps, riverbanks, bayous, canals, ditches, estuaries, lakeshores, hammocks +
terminal +  and axillary +
0.2 cm2 mm <br />0.002 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +
reduced +
scarious +  and membranaceous +
well-developed +
Flowering summer–fall. +
rudimentary +
reddish-brown +  and dark-brown +
1mm;1.2mm +
lenticular +  and subglobose +
Weedy +  and Illustrated +
well-developed +
stout;robust +
prostrate +  and decumbent +
150 cm1,500 mm <br />1.5 m <br /> (300 cm3,000 mm <br />3 m <br />) +
not fleshy +
slender +
0.01 cm0.1 mm <br />1.0e-4 m <br /> (0.1 cm1 mm <br />0.001 m <br />) +
Acnida alabamensis +, Acnida cannabina var. australis +  and Acnida cuspidata +
Amaranthus australis +
Amaranthus sect. Acnida +
species +
distinct +
linear-lanceolate +  and reduced-linear +
subequal +
indurate +, membranaceous +, chartaceous +  and scarious +
walled +  and 3(-5)-veined +
stramineous +  and brown +
tuberculate +  and rugose +
obovoid +  and elliptic +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.25 cm2.5 mm <br />0.0025 m <br />) +