Ageratina occidentalis

(Hooker) R. M. King & H. Robinson
Phytologia 19: 224. 1970.
Common names: Western snakeroot
IllustratedEndemic
Basionym: Eupatorium occidentale Hooker Fl. Bor.-Amer. 1: 305. 1833
Treatment appears in FNA Volume 21. Treatment on page 552. Mentioned on page 547, 548.

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. Heads clustered. Peduncles 2–5 mm, minutely puberulent. Involucres 3–3.5(–4) mm. Phyllaries: apices acute, abaxial faces viscid-puberulent and/or sessile-glandular. Corollas pink, bluish, or white tinged with purple, lobes glabrous or glabrate. Cypselae sessile-glandular. 2n = 34.


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

Distribution

V21-1402-distribution-map.gif

Calif., Idaho, Mont., Nev., Oreg., Utah, Wash.

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.

Selected References

None.

Lower Taxa

None.

... more about "Ageratina occidentalis"
Guy L. Nesom +
(Hooker) R. M. King & H. Robinson +
Eupatorium occidentale +
Western snakeroot +
Calif. +, Idaho +, Mont. +, Nev. +, Oreg. +, Utah +  and Wash. +
(40–50)900–2800(–3200) m +
Crevices, outcrops, rocky slopes, ridges, talus, gravelly and sandy stream bars, mixed hardwood-conifer woodlands, aspen, open and brushy vegetation +
Flowering (Jun–)Jul–Sep. +
Illustrated +  and Endemic +
Compositae +
Ageratina occidentalis +
Ageratina +
species +