Ageratina occidentalis

(Hooker) R. M. King & H. Robinson

Phytologia 19: 224. 1970

Common names: Western snakeroot
Basionyms: Eupatorium occidentale Hooker Fl. Bor.-Amer. 1: 305. 1833
Treatment appears in FNA Volume 21. Treatment on page 552. Mentioned on page 547, 548.
Click plate for higher resolution version.
Illustrator: Linny Heagy
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.

References

None.

Lower Taxa

No lower taxa listed.

AuthorGuy L. Nesom +
Authority(Hooker) R. M. King & H. Robinson +
BasionymsEupatorium occidentale +
Common nameWestern snakeroot +
DistributionCalif. +, Idaho +, Mont. +, Nev. +, Oreg. +, Utah + and Wash. +
Elevation(40–50)900–2800(–3200) m +
HabitatCrevices, outcrops, rocky slopes, ridges, talus, gravelly and sandy stream bars, mixed hardwood-conifer woodlands, aspen, open and brushy vegetation +
IllustratorLinny Heagy +
PhenologyFlowering (Jun–)Jul–Sep. +
Publication titlePhytologia +
Publication year1970 +
ReferenceNone +
Source xmlhttps://jpend@bitbucket.org/aafc-mbb/fna-data-curation.git/src/f6b125a955440c0872999024f038d74684f65921/coarse grained fna xml/V19-20-21/V21 1402.xml +
SynonymsCompositae +
Taxon familyAsteraceae +
Taxon nameAgeratina occidentalis +
Taxon parentAgeratina +
Taxon rankspecies +
VolumeVolume 21 +