Khakiweed

For the nomenclautre of Alternanthera sessilis and Alternanthera pungens, see Melville in Kew Bull. 1958: 171-174. 1958.

One of us (Clemants) notes that the name Alternanthera pungens has been misapplied here and that this taxon should instead be treated as A. caracasana Humboldt et al.

Alternanthera pungens was long known as A. repens (Linnaeus) Link, a later homonym of A. repens J. F. Gmelin.

Prostrate mat-forming perennial herb with a stout vertical rootstock, also rooting at the lower nodes, much-branched from the base outwards, mats up to c. 1 m across. Stem and branches terete, striate, ± densely villous with long, white hairs but frequently glabrescent. Leaves broadly rhomboid-ovate to broadly oval or obovate, 1.5-4.5 x 0.3-2.7 cm, rounded to subacute at the apex with a mucro which in the young leaves is often fine and bristle-like, narrowed below to a petiole up to 1 cm long, glabrous or thinly appressed-pilose on both surfaces, especially on the lower surface of the primary venation. Inflorescences sessile, axillary, solitary or more commonly 2-3 together, globose to shortly cylindrical, 0.5-1.5 cm long and 0.5-1 cm wide; bracts membranous, white or stramineous, 4-5 mm, lanceolate-ovate, glabrous or dorsally pilose, distinctly aristate with the excurrent midrib, strongly denticulate around the upper margin; bracteoles similar but smaller, 3-4 mm, falling with the fruit. Tepals extremely dissimilar; the 2 outer (abaxial) deltoid-lanceolate, 5 mm, very rigid, 5-nerved below (the intermediate pair of nerves much shorter and finer), outer 2 nerves meeting above to join the excurrent, pungently mucronate midrib; inner (adaxial) tepal oblong, flat, 3 mm, blunt and strongly dentate at the apex, 3-nerved below but the nerves meeting well below the apex and the apical mucro short and fine; lateral tepals c. 3 mm, sinuate in side view with the two sides of the lamina connivent and denticulate above, sharply mucronate; abaxial and adaxial tepals with small tufts of glochidiate and barbed whitish bristles about the basal angles, the lateral tepals each with a large tuft about the centre of the midrib. Stamens 5, all with anthers, at anthesis slightly exceeding the ovary and style, the alternating pseudostaminodes broad, subquadrate, shorter than the filaments, entire to dentate. Ovary compressed, squat, narrowed below, style very short, wider than long. Fruit orbicular, rounded or retuse above, 2 mm. Seed discoid, c. 1.25 m, brown, shining faintly reticulate.

Herbs annual. Stem diffuse, creeping, much branched, 20-30 cm tall, densely rigidly hairy. Petiole 3-10 mm, glabrous or hairy; leaf blade ovate, obovate, or elliptic-obovate, 1.5-4.5 × 0.5-1.5 cm, unequal in each pair, glabrous or annexed pilose, base acuminate, apex obtuse. Heads sessile, 1-3, axillary, white, globose or oblong, 5-10 mm. Bracts lanceolate, ca. 4 mm, spiny at apex; bracteoles lanceolate, 3-4 mm, apex acuminate, without spines. Tepals unequal, outer 2 lanceolate, ca. 5 mm, 3-veined below, rigid after anthesis, midvein stretching into spines; central segment elliptic, 3-3.5 mm, compressed; inner 2 small, enclosing ovary. Stamens 5; filaments 0.5-0.8 mm; pseudostaminodes shorter than filaments, entire or irregularly dentate. Style very short. Utricles brown, broadly ellipsoid, 1-1.5 mm. Fl. May, fr. Jul.

Herbs, perennial, 3-8 dm. Stems prostrate, villous. Leaves sessile; blade oval to obovate, usually as broad as long, 1.3-3 × 1.1-1.7 cm, apex rounded, pilose, glabrate. Inflorescences axillary, sessile; heads stramineous, globose to ovoid, 0.6-1 × 0.6-0.7 cm; bracts equaling tepals, apex attenuate. Flowers: tepals dimorphic, stramineous, lanceolate, 5-7 mm, apex acuminate, spinose tipped, sparsely villous, hairs barbed; stamens 5; anthers 3-5, globose; pseudostaminodes triangular, shorter than filaments, margins dentate. Utricles included within tepals, brown, compressed, 1.8 mm, apex truncate. Seeds lenticular, 1.3-1.5 mm.

introduced; Ala., Fla., La., N.Y., Tex.; West Indies; South America.

Distribution: A native of tropical America, now widespread as a weed of waste ground etc. in the tropics and subtropics of both Old and New Worlds. Seems to thrive in bare, heavily trodden places.

Flowering summer-fall.

Waste grounds, cleared limestone areas; 0-1500m.

Roadsides. Fujian, Sichuan [native to South America; naturalized in Bhutan, Myanmar, Thailand, ?other parts of Indo-China, Australia, and United States].

Achyranthes repens Linnaeus; Alternanthera repens (Linnaeus) Link.

Achyranthes leiantha (Seubert) Standley

pungens: prickly, puncturing

Prostrate, mat-forming herb, growing from a tap root. Stems rooting at the nodes. Inflorescences somewhat spiny, due to long bracteoles and awns on the tepals.

Native of tropical America, now a widespread weed in Africa

Achyranthes obovata (Mart. & Gal.) Standley, Jour. Wash
Acad. Sci. 5: 74. 1915.
Bucholzia obovata Mart. & Gal. Bull. Acad. Brux, 10 1 : 348. 1843. Telanthera obovata Moq. in DC. Prodr. 132: 370. 1849.
Gomphrena procumbens Pavon; Moq. in DC. Prodr. 13 2 : 370, as synonym. 1849. Not G. procumbens Zucc. 1809.
Perennial, sometimes suffrutescent at the base; stems prostrate or decumbent, 2-10
dm, long, rooting at the nodes, much branched, the branches erect or ascending, stout, densely
villous when young, glabrate in age; petioles 5 mm. long or less, the upper leaves subsessile;
i
leaf-blades rounded-obovate to broadly oval, cuneate-obovate, or oblong, 1.5-4.5 cm. long, 0.7-2 cm. wide, rounded or obtuse at the apex, cuneate to rounded at the base, thick, brightgreen, villous when young, glabrate in age; spikes axillary or terminal, sessile, solitary, subglobose to cylindric, 1.2-3.5 cm. long, 1 cm. thick, the flowers yellowish-white; bracts and bractlets broadly ovate, half as long as the sepals, acuminate, mucronulate, hyaline, glabrous, serrulate near the apex; sepals oblong, 4 mm. long, acute, serrulate at the apex, 1 -nerved, glabrous; filaments linear, the tube about as long as the ovary; staminodia linear, acutish, entire, longer than the filaments, two thirds as long as the sepals ; style short.
Type locality: On dry and volcanic rocks of the barranca of I,os Banos, near the hot spring of Acasonica, Vera Cruz, Mexico.
Distribution: Tamaulipas to Guatemala.

Achyranthes leiantha (Seub.) Standley, Jour. Wash. Acad. Sci
5: 73. 1915.
Alternanthera pungens H. B. K. Nov. Gen. & Sp. 2: 206. 1817. Not Achyranthes pungens Lam.
1783. Celosia echinata Humb. & Bonpl.; R. & S. Syst. Veg. 5: 531. 1819. Not Achyranthes echinata
Retz. 1781. Illecebrum pungens Spreng. Syst. 1: 820. 1825. Telanthera pungens Moq. in DC. Prodr. 13 2 : 371. 1849. Alternanthera Achyrantha leiantha Seub. in Mart. Fl. Bras. 5 1 : 183.
1875.
Stems prostrate, 3-8 dm. long, stout, much branched, villous with obscurely scaberulous white hairs; petioles 2-5 mm. long, margined; leaf-blades orbicular, rhombic-orbicular, or broadly oval, 1.3-5 cm. long, rounded at the apex, apiculate and mucronate, firm, prominently veined, appressed-pilose when young but soon glabrate; heads axillary, solitary, sessile, 8-10 mm. long; bracts and bractlets lance-oblong, equaling the perianth, attenuate to an aristate apex, glabrous; sepals oblong or ovateoblong, 5-6 mm. long, acuminate to a long-aristate rigid tip, 3-nerved, stramineous, sparsely villous near the base and along the nerves, the inner sepals narrower and shorter than the outer ones; filaments linear, the staminodia slightly shorter, triangular, remotely dentate; style short; utricle strongly compressed, truncate; seed 1.5 mm. long, dark-brown.
Typb locality: Banks of the Orinoco near the cataract of Maipures, Venezuela. Distribution: Adventive in southern Florida and Alabama; eastern Mexico; Cuba and Jamaica; also from Venezuela to Bolivia and Uruguay.

Illustration from Hortus Elthamensis Illustration from Histoire naturelle des Iles Canaries

Alternanthera pungens is a creeping, prostrate perennial pioneer plant of the family Amaranthaceae, spreading by seed and vegetatively, with roots often developing at the nodes of spreading stems. A plant of roadsides, path verges and waste places (ruderal), it is thought to have come from Central and South America, and to have become widely established in Australia and Southern Africa. Other species of this genus, e.g. Alternanthera sessilis (L.) R.Br. ex DC., have long been recorded from Tropical Africa, and would be difficult to prove as invaders.

The species forms dense mats of stems and leaves during the rainy season. During the dry season or in drought, material above ground dies off and the dormant plant is sustained by its fleshy taproot. Clusters of small white flowers form in the leaf axils. The small, khaki-coloured, prickly, papery fruits are stemless, form in the leaf axils and are spread by stock, vehicles and in stock feed. The shiny seeds are brownish, compressed, lenticular and about 1.5 mm across.

The species was illustrated as far back as 1732 by Johann Jacob Dillenius in his Hortus Elthamensis, vol. 1, and described as "Achyracantha repens foliis Bliti pallidi", and again in 1836 by Jean-Christophe Heyland (1792-1866) in Histoire naturelle des Iles Canaries, vol. 2(3): p. 193, t. 199 (1836). Kew currently lists 139 species in the genus Alternanthera.