Ageratina adenophora |
Ageratina altissima |
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Crofton weed, eupatory, Mexican devil, sticky snakeroot, thoroughwort |
white snakeroot |
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Habit | Subshrubs, 50–220 cm. | Perennials, (30–)50–80(–120) cm (bases usually fibrous-rooted crowns, sometimes rhizomatous). | ||||
Stems | (usually purplish when young) erect, stipitate-glandular. |
ascending to erect, sometimes semiscandent, puberulent (hairs minute, crisped). |
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Leaves | opposite; petioles 10–25 mm; blades (abaxially purple) ovate-lanceolate or ovate-deltate to lanceolate-ovate, (1.5–)2.5–5.5(–8) × 1.5–4(–6) cm, bases cuneate to obtuse or nearly truncate, margins serrate, apices acute to acuminate, abaxial faces stipitate- to sessile-glandular. |
opposite; petioles (5–)10–30(–50) mm; blades usually deltate-ovate to ovate or broadly lanceolate, sometimes ovate-lanceolate, 4–11(–13) × 2.5–8(–9) cm, bases usually rounded to truncate or obtuse, sometimes cordate, margins coarsely and doubly incised-serrate, apices usually acuminate. |
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Peduncles | 5–12 mm, densely stipitate-glandular and sometimes also sparsely viscid-puberulent. |
1–5 mm, puberulent. |
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Involucres | 3.5–4 mm. |
4–5 mm. |
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Corollas | white, pink-tinged, lobes sparsely hispidulous. |
white, lobes sparsely short-villous. |
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Phyllaries | apices acute, abaxial faces stipitate-glandular. |
apices acute, abaxial faces glabrous or sparsely and finely villous. |
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Heads | clustered. |
clustered. |
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Cypselae | glabrous. |
glabrous. |
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2n | = 51. |
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Ageratina adenophora |
Ageratina altissima |
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Phenology | Flowering Mar–Aug(–Sep). | |||||
Habitat | Stream margins, ditches, road embankments, hillsides | |||||
Elevation | 400–900 m (1300–3000 ft) | |||||
Distribution |
CA; Mexico; Intoduced [Also introduced in Europe, Pacific Islands (New Zealand)]
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AL; AR; CT; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NY; OH; OK; PA; RI; SC; SD; TN; TX; VA; VT; WI; WV; NB; NS; ON; QC; SK
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Discussion | Varieties 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 553. | FNA vol. 21, p. 549. | ||||
Parent taxa | ||||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Eupatorium adenophorum | Ageratum altissimum | ||||
Name authority | (Sprengel) R. M. King & H. Robinson: Phytologia 19: 211. (1970) | (Linnaeus) R. M. King & H. Robinson: Phytologia 19: 212. (1970) | ||||
Web links |