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 glanddotted. 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.

"fine" is not a number.

... more about "Ageratina occidentalis"
sessile-glandular +  and viscid-puberulent +
not tailed +, truncate +, rounded +  and obtuse +
scarious +
usually ovate +  and lanceolate +
usually terete +  and clavate +
indeterminate +  and determinate +
Guy L. Nesom +
(Hooker) R. M. King & H. Robinson +
truncate +  and cuneate +
enlarged +
Eupatorium occidentale +
3(-5)-nerved +
2.5 cm25 mm <br />0.025 m <br /> (5 cm50 mm <br />0.05 m <br />) +
dissected +, lobed +, toothed +  and entire +
triangular;ovate +
1.7cm;4cm +
papillate +  and rugose +
(4-)5-angled;10-ribbed +
Western snakeroot +
white tinged with purple +, bluish +  and pink +
scabrellous +
fusiform +  and prismatic +
fertile +  and bisexual +
Calif. +, Idaho +, Mont. +, Nev. +, Oreg. +, Utah +  and Wash. +
(40–50)900–2800(–3200) m +
puberulent +, pilose +, hispidulous +  and glabrous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
Crevices, outcrops, rocky slopes, ridges, talus, gravelly and sandy stream bars, mixed hardwood-conifer woodlands, aspen, open and brushy vegetation +
indeterminate +
each +  and sessile +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
0.3 cm3 mm <br />0.003 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
campanulate +
0.3 cm3 mm <br />0.003 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
alternate +  and opposite +
glabrate +  and glabrous +
lanceolate +  and lance-linear +
2-carpellate +
persistent +
0.2 cm2 mm <br />0.002 m <br /> (0.5 cm5 mm <br />0.005 m <br />) +
0.5 cm5 mm <br />0.005 m <br /> (1.2 cm12 mm <br />0.012 m <br />) +
Flowering (Jun–)Jul–Sep. +
2-nerved +  and 0-nerved +
8 +  and 30 +
subequal +  and unequal +
bearing subulate enations +, hairy +  and bristly +
exalbuminous +
Illustrated +  and Endemic +
ascending +  and erect +
appendaged +  and truncate +
hirsutulous +
papillate +
Compositae +
Ageratina occidentalis +
Ageratina +
species +
obconic +  and campanulate +
15 cm150 mm <br />0.15 m <br /> (70 cm700 mm <br />0.7 m <br />) +