Description :

• Annual or perennial herbs or subshrubs
• Leaves opposite or upper alternate, entire or dentate, with large glandular spots on lower surface
• Capitula discoid; many-flowered, in dense corymbs or occasionally a lax panicle
• Involucre campanulate; bracts in 2 or 3 rows, free, ribbed, with membranous margins
• Receptacle honeycombed, conical, naked or paleate
• Corolla purple, blue or white; tube cylindric below, campanulate above; lobes 5, much shorter than tube, glandular
• Anthers obtuse at base, with oblong, apical appendage
• Style terete, with short glandular branches
• Cypselas 4- or 5-ribbed, glabrous or short-setose on ribs; carpopodium usually large and asymmetrical
• Pappus coroniform, of 5 or 6 free scales or awns or 0
• x = 10 (aneuploids, polyploidy)

Nomenclature:

• *Ageratum L.
  • Linnaeus: 839 (1753)
  • Linnaeus: 363 (1754)
  • Harvey: 57 (1865)
  • Oliver & Hiern: 300 (1877)
  • Phillips: 777 (1951)
  • Johnson: 13 (1971)
  • Hilliard: 50 (1977)
  • Bremer et al.: 649 (1994)

Distribution & Notes:

• Global : Species 44, all natives of Central and South America, the West Indies
• Southern Africa : Species 2, naturalised: * Ageratum conyzoides L. occurring in the Northern Province and Mpumalanga, and *A. houstonianum Mill., known from KwaZulu-Natal and Eastern Cape