Alternanthera sessilis |
Alternanthera philoxeroides |
|
---|---|---|
sessile joyweed |
alligator weed, pig weed |
|
Habit | Herbs, annual or perennial, 2–6 dm. | Herbs, perennial, aquatic to semiterrestrial, stoloniferous, to 50 dm. |
Stems | procumbent, pubescent in lines, glabrate. |
prostrate, forming mats, often fistulose, glabrous. |
Leaves | sessile; blade elliptic to oblong or oblanceolate, 1.2–5 × 0.5–2.2 cm, apex obtuse to acute, glabrous. |
sessile; blade narrowly elliptic, elliptic, or oblanceolate, 3.5–7.1 × 0.5–2 cm, herbaceous, apex acute to obtuse, glabrous. |
Inflorescences | axillary, sessile; heads white, subglobose or ovoid, 0.5–1.1 cm; bracts keeled, ca. 1/2 as long as tepals. |
terminal and axillary, pedunculate; heads white, globose, 1.4–1.7 cm diam.; bracts not keeled, less than 1/2 as long as tepals. |
Flowers | tepals white, ovate to lanceolate, 2–3.5 mm, apex acuminate, hairs not barbed; stamens 5; anthers 3–5, globose; pseudostaminodes subulate, margins laciniate. |
tepals monomorphic, white, lanceolate or oblong, 6 mm, apex acute, glabrous; stamens 5; pseudostaminodes ligulate. |
Seeds | lenticular, 0.9–1.1 mm. |
not seen. |
Utricles | included within tepals, sides exerted in mature fruit, greenish stramineous, obcordate, 1.3–1.7 mm, apex retuse. |
not seen. |
Alternanthera sessilis |
Alternanthera philoxeroides |
|
Phenology | Flowering summer–early fall. | Flowering early spring–summer. |
Habitat | Wet disturbed areas | Ponds, ditches, streams, bayous |
Elevation | 0-20 m (0-100 ft) | 0-200 m (0-700 ft) |
Distribution |
Mexico; South America; West Indies; Central America (Belize, Costa Rica, Guatemala, Nicaragua, Panama); Africa; Asia [Introduced, Ala., Fla., Ga., La.]
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AL; AR; CA; FL; GA; IL; KY; LA; MS; NC; SC; TN; TX; VA; West Indies; native to South America [Introduced in North America]
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Discussion | Alternanthera sessilis is reported from Maryland, Mississippi, South Carolina, and Texas, but I have seen no specimens from these states. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Alternanthera philoxerioides is said to reproduce only vegetatively in North America. I have seen no fruit or seed. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 4, p. 450. | FNA vol. 4, p. 448. |
Parent taxa | Amaranthaceae > Alternanthera | Amaranthaceae > Alternanthera |
Sibling taxa | ||
Synonyms | Gomphrena sessilis | Bucholzia philoxeroides, Achyranthes philoxeroides |
Name authority | (Linnaeus) R. Brown ex de Candolle: Cat. Pl. Hort. Monsp., 77. (1813) | (Martius) Grisebach: Abh. Königl. Ges. Wiss. Göttingen 24: 36. (1879) |
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