Ageratum conyzoides |
Ageratum |
|||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
tropical whiteweed |
whiteweed |
|||||||||||||
Habit | Annuals, perennials, or sub-shrubs, 20–150 cm (fibrous-rooted). | Annuals and perennials, mostly 20–120 cm. | ||||||||||||
Stems | erect, sparsely to densely villous. |
often decumbent (rooting at proximal nodes), sparsely to densely branched. |
||||||||||||
Leaves | blades ovate to elliptic-oblong, 2–8 × 1–5 cm, margins toothed, abaxial faces sparsely pilose and gland-dotted. |
cauline; all or mostly opposite; petiolate; blades mostly 1-nerved, deltate to ovate, or elliptic to lanceolate, margins entire or toothed, faces glabrous or ± pilose, puberulent, or strigoso-hispid, sometimes gland-dotted. |
||||||||||||
Peduncles | minutely puberulent and sparsely to densely pilose, eglandular. |
|||||||||||||
Involucres | 3–3.5 × 4–5 mm. |
campanulate, 3–6 mm. |
||||||||||||
Receptacles | conic, epaleate [paleate]. |
|||||||||||||
Florets | 20–125; corollas white or bluish to lavender, throats ± campanulate (lengths 2 times diams.); styles: bases not enlarged, glabrous, branches ± linear to clavate (usually papillose and dilated distally). |
|||||||||||||
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. |
persistent, 30–40 in 2–3 series, usually 2-nerved, lanceolate, ± equal (often indurate, margins scarious). |
||||||||||||
Heads | discoid, in dense to open, cymiform to corymbiform arrays. |
|||||||||||||
Cypselae | sparsely strigoso-hispidulous; pappi usually of scales 0.5–1.5(–3) mm, sometimes with tapering setae, rarely 0. |
prismatic, 4–5-ribbed, glabrous or sparsely strigoso-hispidulous; pappi persistent, of 5–6 aristate scales, or coroniform, or 0. |
||||||||||||
x | = 10. |
|||||||||||||
2n | = 20, 40. |
|||||||||||||
Ageratum conyzoides |
Ageratum |
|||||||||||||
Phenology | Flowering Jul–Aug. | |||||||||||||
Habitat | Disturbed sites, mostly coastal | |||||||||||||
Elevation | 0–20 m (0–100 ft) | |||||||||||||
Distribution |
AL; CA; CT; FL; GA; KY; MD; MO; MS; NC; HI; Central America; South America; West Indies [Introduced in North America; introduced, Mexico] |
United States; Mexico; Central America; 2 species widespread as adventives |
||||||||||||
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.) |
Species ca. 40 (4 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
||||||||||||
Key |
|
|||||||||||||
Source | FNA vol. 21, p. 482. | FNA vol. 21, p. 481. | ||||||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Ageratum | Asteraceae > tribe Eupatorieae | ||||||||||||
Sibling taxa | ||||||||||||||
Subordinate taxa | ||||||||||||||
Synonyms | A. latifolium | |||||||||||||
Name authority | Linnaeus: Sp. Pl. 2: 839. (1753) | Linnaeus: Sp. Pl. 2: 839. (1753): Gen. Pl. ed. 5, 363. (1754) | ||||||||||||
Web links |