Flora of North America species comparison

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Ageratum conyzoides

tropical whiteweed
Habit 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.
Corollas

usually blue to lavender, sometimes white.
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.
Cypselae

sparsely strigoso-hispidulous;

pappi usually of scales 0.5–1.5(–3) mm, sometimes with tapering setae, rarely 0.
2n

= 20, 40.

Ageratum conyzoides
Phenology Flowering Jul–Aug.
Habitat Disturbed sites, mostly coastal
Elevation 0–20 m [0–70 ft]
Distribution
from FNA
AL; CA; CT; FL; GA; KY; MD; MO; MS; NC; HI; Central America; South America; West Indies [Introduced in North America; introduced, Mexico]
[BONAP county map]
Discussion

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

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 482.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratum
Sibling taxa
A. corymbosum, A. houstonianum, A. maritimum
Synonyms A. latifolium
Name authority Linnaeus: Sp. Pl. 2: 839. (1753)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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