Ageratum conyzoides


Sp. Pl. 2: 839. 1753.

Common names: Tropical whiteweed
Synonyms: Ageratum latifolium Cavanilles
Treatment appears in FNA Volume 21. Treatment on page 482. Mentioned on page 483.

Annuals, perennials, or sub-shrubs, 20–150 cm (fibrous-rooted). Stems erect, sparsely to densely villous. Leaf blades ovate to elliptic-oblong, 2–8 × 1–5 cm, margins toothed, abaxial faces sparsely pilose and gland-dotted. Peduncles minutely puberulent and sparsely to densely pilose, eglandular. Involucres 3–3.5 × 4–5 mm. Phyllaries oblong-lanceolate (0.8–1.2 mm wide), glabrous or sparsely pilose (margins often ciliate), eglandular, tips abruptly tapering, subulate, 0.5–1 mm. Corollas usually blue to lavender, sometimes white. Cypselae sparsely strigoso-hispidulous; pappi usually of scales 0.5–1.5(–3) mm, sometimes with tapering setae, rarely 0. 2n = 20, 40.

Phenology: Flowering Jul–Aug.
Habitat: Disturbed sites, mostly coastal
Elevation: 0–20 m



Introduced; Ala., Calif., Conn., Fla., Ga., Ky., Md., Miss., Mo., N.C., South America, introduced, Mexico, West Indies, Central America, Pacific Islands (Hawaii).


Ageratum conyzoides is apparently native to South America. North American plants were escapes and naturalized from cultivation.

Selected References


Lower Taxa

... more about "Ageratum conyzoides"
Guy L. Nesom +
Linnaeus +
Tropical whiteweed +
Ala. +, Calif. +, Conn. +, Fla. +, Ga. +, Ky. +, Md. +, Miss. +, Mo. +, N.C. +, South America +, introduced +, Mexico +, West Indies +, Central America +  and Pacific Islands (Hawaii). +
0–20 m +
Disturbed sites, mostly coastal +
Flowering Jul–Aug. +
Introduced +
Ageratum latifolium +
Ageratum conyzoides +
Ageratum +
species +