Amaranthus australis (A. Gray) Sauer

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.

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.

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

Flowering summer-fall.

Freshwater and brackish wetland habitats, coastal marshes, swamps, riverbanks, bayous, canals, ditches, estuaries, lakeshores, hammocks; 0-100m.

Acnida australis A. Gray, Amer. Naturalist 10: 489. 1876; A. alabamensis Standley; A. cannabina Linnaeus var. australis (A. Gray) Uline & W. L. Bray; A. cuspidata Bertero ex Sprengel

Acnida cuspidata Bert.; Spreng. Syst. Veg. 3: 903. 1826
Acnida cannabina cuspidata Moq. in DC. Prodr, 13 2 : 277, Acnida australis A. Gray, Am. Nat. 10: 489. 1876. Acnida cannabina australis Uline & Bray, Bot. Gaz. 20: 157.
1849.
1895.
Plants glabrous throughout; stems stout, erect, 1-7 m. high, usually much thickened at the base, smooth, succulent, much branched above; leaves numerous, the petioles slender, 2-20 cm. long, the blades narrowly lanceolate to ovate, 6-30 cm. long, 1.5-14 cm. wide, acuminate or long-attenuate at the apex, rounded to acute at the base, undulate, yellowishor bright-green, prominently nerved; staminate flowers in narrow, leafy or naked panicles composed of numerous slender, erect or drooping, densely flowered spikes 3-9 cm. long and 6 mm. thick; pistillate flowers in narrow, elongate, axillary and terminal, naked or leafy panicles of slender, erect or drooping, loosely flowered spikes 6-15 cm. long and 5-7 mm. thick; sepals ovate or oval, 3 mm. long,. acute, scarious, 1-nerved, with spreading mucronate tips, twice as long as the broadly' ovate scarious bracts; bracts of the pistillate flowers equaling or longer than the utricle, ovate to subulate, rigid, attenuate to a pungent tip, green; stigmas 3-5, short and stout; utricle obovoid or turbinate, 1.5-2.5 mm. long, fleshy, indehiscent, 3-5-angled; seed flattened, 1 mm.' in diameter, rotund or obovate, minutely granulate, nearly black.
Type locality: Jamaica.
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Amaranthus australis is also known as southern amaranth or southern water-hemp. The plant usually grows from 1 to 3 m (3.3 to 9.8 ft) in height, though some have been known to grow up to 9 m (30 ft) high. The stems can be up to 30 cm in diameter. It is a herbaceous annual. It is found in many southern states of the United States, Mexico, the West Indies, and South America. They are frequently found in wetland areas. It is herbaceous, short lived perennial. The largest is 4.6 m (15 ft) tall.

Amaranthus australis es una especie de planta herbácea perteneciente a la familia Amaranthaceae.

Amaranthus australis là loài thực vật có hoa thuộc họ Dền. Loài này được (A.Gray) Sauer mô tả khoa học đầu tiên năm 1955.