Ageratum houstonianum |
Ageratum conyzoides |
|
---|---|---|
bluemink, floss flower, Houston's whiteweed |
tropical whiteweed |
|
Habit | Annuals, 30–80 cm (fibrous-rooted). | Annuals, perennials, or sub-shrubs, 20–150 cm (fibrous-rooted). |
Stems | erect to decumbent, sparsely to densely pilose. |
erect, sparsely to densely villous. |
Leaf | blades deltate to ovate, mostly 3–8 × 2.5–4 cm, margins toothed, abaxial faces sparsely to densely pilose, not evidently gland-dotted. |
blades ovate to elliptic-oblong, 2–8 × 1–5 cm, margins toothed, abaxial faces sparsely pilose and gland-dotted. |
Peduncles | viscid-puberulent, pilose, and stipitate-glandular. |
minutely puberulent and sparsely to densely pilose, eglandular. |
Involucres | ca. 4 × 5–6 mm. |
3–3.5 × 4–5 mm. |
Corollas | usually lavender, rarely white. |
usually blue to lavender, sometimes white. |
Phyllaries | narrowly lanceolate (0.6–1 mm wide), stipitate-glandular, sparsely to densely pilose, eciliate or inconspicuously ciliate, tips gradually tapering, indurate-subulate, 0.8–2 mm. |
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 of 5 distinct, oblong scales 2–3 mm. |
sparsely strigoso-hispidulous; pappi usually of scales 0.5–1.5(–3) mm, sometimes with tapering setae, rarely 0. |
2n | = 20. |
= 20, 40. |
Ageratum houstonianum |
Ageratum conyzoides |
|
Phenology | Flowering Jun–Aug. | Flowering Jul–Aug. |
Habitat | Disturbed sites, mostly coastal | Disturbed sites, mostly coastal |
Elevation | 0–20 m (0–100 ft) | 0–20 m (0–100 ft) |
Distribution |
AL; CT; FL; GA; MA; NC; SC; TX; Mexico; Central America [Introduced in North America; introduced, Pacific Islands (Hawaii)]
|
AL; CA; CT; FL; GA; KY; MD; MO; MS; NC; HI; Central America; South America; West Indies [Introduced in North America; introduced, Mexico] |
Discussion | Ageratum houstonianum is apparently native to southeastern Mexico and Central America; the North American plants are escapes and naturalized from cultivars. M. F. Johnson (1971) observed that forma isochroum (B. L. Robinson) M. F. Johnson (type from the state of Veracruz, Mexico) sometimes may be nearly eglandular. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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. 483. | FNA vol. 21, p. 482. |
Parent taxa | Asteraceae > tribe Eupatorieae > Ageratum | Asteraceae > tribe Eupatorieae > Ageratum |
Sibling taxa | ||
Synonyms | A. conyzoides var. mexicanum | A. latifolium |
Name authority | Miller: Gard. Dict. ed. 8, Ageratum no. 2. (1768) | Linnaeus: Sp. Pl. 2: 839. (1753) |
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