Flora of North America species comparison

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Ageratina aromatica

Ageratina occidentalis

lesser snakeroot, small-leaf white snakeroot

western boneset, western eupatorium, western snakeroot
Habit Perennials, 30–80(–100) cm. Perennials or subshrubs, 15–70 cm (caudices woody, rhizomatous).
Stems

erect, villous-puberulent.

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

opposite;

petioles 1–8(–12) mm;

blades narrowly to broadly deltate to nearly ovate or lanceolate, 2–7(–9) × 1.5–4 cm, (usually subcoriaceous) bases rounded or truncate to barely cuneate or subcordate, margins usually crenate, sometimes crenate-serrate to dentate or subentire, apices acute to obtuse, faces minutely pilose.

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

2–9 mm, densely and closely puberulent.

2–5 mm, minutely puberulent.
Involucres

3.5–5 mm.

3–3.5(–4) mm.
Corollas

white, lobes sparsely villous.

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

apices acute, abaxial faces puberulent to villous-puberulent.

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

clustered.

clustered.
Cypselae

usually glabrous or sparsely puberulent (near apices), rarely hirtellous on angles.

sessile-glandular.
2n

= 34.

= 34.

Ageratina aromatica

Ageratina occidentalis
Phenology Flowering late Aug–Oct(–Nov). Flowering (Jun–)Jul–Sep.
Habitat Sandy soils, burned pinelands, turkey oak sand ridges, pine-oak and oak-hickory upland woods, old fields, roadsides, fencerows, moist sites Crevices, outcrops, rocky slopes, ridges, talus, gravelly and sandy stream bars, mixed hardwood-conifer woodlands, aspen, open and brushy vegetation
Elevation 100–900 m (300–3000 ft) (40–50)900–2800(–3200) m ((100–200)3000–9200(–10500) ft)
Distribution
from FNA
AL; CT; DE; FL; KY; LA; MA; MD; MS; NC; NJ; NY; OH; PA; RI; SC; TN; VA; WV
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; MT; NV; OR; UT; WA
[WildflowerSearch map]
[BONAP county map]
Discussion

Intergrades (probable hybrids) between Ageratina aromatica and A. altissima were identified by A. F. Clewell and J. W. Wooten (1971) over a broad area of their sympatry. They also found intergrades between A. aromatica and A. jucunda where their ranges meet.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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. 550. FNA vol. 21, p. 552.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratina Asteraceae > tribe Eupatorieae > Ageratina
Sibling taxa
A. adenophora, A. altissima, 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 aromaticum, Eupatorium latidens Eupatorium occidentale
Name authority (Linnaeus) Spach: Hist. Nat. Vég. 10: 286. (1841) (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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