Flora of North America species comparison

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Ageratina adenophora

Ageratina occidentalis

Crofton weed, eupatory, Mexican devil, sticky snakeroot, thoroughwort

western boneset, western eupatorium, western snakeroot
Habit Subshrubs, 50–220 cm. Perennials or subshrubs, 15–70 cm (caudices woody, rhizomatous).
Stems

(usually purplish when young) erect, stipitate-glandular.

(green or purple) erect or ascending, puberulent.
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 proximally, alternate on distal 1/4–1/2 of stems;

petioles 5–12 mm;

blades triangular to ovate, 2.5–5 × 1.7–4 cm, bases truncate to cuneate, margins serrate, apices acute, abaxial faces gland-dotted.
Peduncles

5–12 mm, densely stipitate-glandular and sometimes also sparsely viscid-puberulent.

2–5 mm, minutely puberulent.
Involucres

3.5–4 mm.

3–3.5(–4) mm.
Corollas

white, pink-tinged, lobes sparsely hispidulous.

pink, bluish, or white tinged with purple, lobes glabrous or glabrate.
Phyllaries

apices acute, abaxial faces stipitate-glandular.

apices acute, abaxial faces viscid-puberulent and/or sessile-glandular.
Heads

clustered.

clustered.
Cypselae

glabrous.

sessile-glandular.
2n

= 51.

= 34.

Ageratina adenophora

Ageratina occidentalis
Phenology Flowering Mar–Aug(–Sep). Flowering (Jun–)Jul–Sep.
Habitat Stream margins, ditches, road embankments, hillsides Crevices, outcrops, rocky slopes, ridges, talus, gravelly and sandy stream bars, mixed hardwood-conifer woodlands, aspen, open and brushy vegetation
Elevation 400–900 m (1300–3000 ft) (40–50)900–2800(–3200) m ((100–200)3000–9200(–10500) ft)
Distribution
from FNA
CA; Mexico; Intoduced [Also introduced in Europe, Pacific Islands (New Zealand)]
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; MT; NV; OR; UT; WA
[WildflowerSearch map]
[BONAP county map]
Discussion

Ageratina occidentalis is the only species of the genus in the flora area with sessile-glandular cypselae; peduncles also may be sessile-glandular. Its identity also can be confirmed among flora area species by its relatively long (5–6 mm) corollas.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 553. FNA vol. 21, p. 552.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratina Asteraceae > tribe Eupatorieae > Ageratina
Sibling taxa
A. altissima, A. aromatica, A. havanensis, A. herbacea, A. jucunda, A. lemmonii, A. luciae-brauniae, A. occidentalis, A. paupercula, A. rothrockii, A. shastensis, A. thyrsiflora, A. wrightii
A. adenophora, A. altissima, A. aromatica, A. havanensis, A. herbacea, A. jucunda, A. lemmonii, A. luciae-brauniae, A. paupercula, A. rothrockii, A. shastensis, A. thyrsiflora, A. wrightii
Synonyms Eupatorium adenophorum Eupatorium occidentale
Name authority (Sprengel) R. M. King & H. Robinson: Phytologia 19: 211. (1970) (Hooker) R. M. King & H. Robinson: Phytologia 19: 224. (1970)
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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