Flora of North America species comparison

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Ageratina occidentalis

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

(green or purple) erect or ascending, puberulent.
Leaves

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

2–5 mm, minutely puberulent.
Involucres

3–3.5(–4) mm.
Corollas

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

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

clustered.
Cypselae

sessile-glandular.
2n

= 34.

Ageratina occidentalis
Phenology Flowering (Jun–)Jul–Sep.
Habitat Crevices, outcrops, rocky slopes, ridges, talus, gravelly and sandy stream bars, mixed hardwood-conifer woodlands, aspen, open and brushy vegetation
Elevation (40–50)900–2800(–3200) m ((100–200)3000–9200(–10500) ft)
Distribution
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. 552.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratina
Sibling taxa
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 occidentale
Name authority (Hooker) R. M. King & H. Robinson: Phytologia 19: 224. (1970)
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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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