Description :

• Coarse, annual herbs, monoecious
• Leaves alternate, petiolate, simple, deltoid or narrowly rhomboidal, margin variously toothed or lobed
• Capitula and florets unisexual
• Male capitula globose, many-flowered; involucre short, bracts few, narrow, in 1 or 2 rows; receptacle hemispherical, paleate; corolla tubular, 5-toothed; anthers with small apical appendage, base obtuse; filaments connate; ovary abortive; style undivided
• Female capitula ovoid, 2-flowered; involucre completely enveloping 2 female flowers, 2-locular within, apex 1- or 2-beaked; corolla 0; style branches long, linear, acute, tips exserted on inner face of each terminal beak near its base; cypselas obovoid or oblong, solitary in each involucral chamber; involucre enlarging, hardening, with prominent hooked spines, shed as 2-celled unit
• Pappus 0
• x = 9 (5, 17) (high polyploidy - 1 report)

Nomenclature:

• *Xanthium L.
  • Linnaeus: 987 (1753)
  • Linnaeus: 424 (1754)
  • Oliver & Hiern: 371 (1877)
  • Phillips: 813 (1951)
  • Wild: 3 (1967)
  • Hilliard: 297 (1977)
  • Henderson et al.: 110 (1987)
  • Karis & Ryding 623 (1994)

Distribution & Notes:

• Global : Species 3, widespread weeds in warm parts of the world
• Southern Africa : Species 2, both from tropical America: * Xanthium spinosum L., widespread but absent from Namibia and Western Cape and * X. strumarium L., troublesome weed, absent from Namibia, Botswana, Northern Province and Northern Cape