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.
... more about "Amaranthus australis"
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 +
1cm;4cm +
elliptic to subulate-linear +  and elliptic +
persistent +
triangular +, deltate +, subulate +, linear +, lanceolate +  and ovate +
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 +
1/3 length of blade +  and 2/3 length of blade +
Flowering summer–fall. +
rudimentary +
0.1 cm1 mm <br />0.001 m <br /> (0.12 cm1.2 mm <br />0.0012 m <br />) +
lenticular +  and subglobose +
Weedy +  and Illustrated +
well-developed +
stout;robust +
prostrate +  and decumbent +
1.5m;3m +
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 />) +