Flora of North America species comparison

The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

Ageratina thyrsiflora

Ageratina aromatica

congested snakeroot

lesser snakeroot, small-leaf white snakeroot
Habit Perennials or subshrubs, 50–100 cm. Perennials, 30–80(–100) cm.
Stems

erect (usually forming compact ‘bushlets’), finely and evenly puberulent (hairs minute, bent).

erect, villous-puberulent.
Leaves

usually alternate, sometimes subopposite (densely overlapping internodes);

petioles 3–20 mm;

blades ovate-lanceolate to triangular, 2.5–6.5 × 1–2.5(–3) cm, bases obtuse to cuneate, margins shallowly and coarsely crenate to serrate to subentire, apices rounded-obtuse, abaxial faces hirtellous.

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.
Peduncles

3–8 mm, puberulent.

2–9 mm, densely and closely puberulent.
Involucres

2.5–3 mm.

3.5–5 mm.
Corollas

white (orange-veined), glabrous.

white, lobes sparsely villous.
Phyllaries

apices acute to obtuse (dark orange-veined), abaxial faces.

apices acute, abaxial faces puberulent to villous-puberulent.
Heads

clustered (in dense, terminal aggregates).

clustered.
Cypselae

hispid.

usually glabrous or sparsely puberulent (near apices), rarely hirtellous on angles.
2n

= 34.

Ageratina thyrsiflora

Ageratina aromatica
Phenology Flowering Sep–Nov. Flowering late Aug–Oct(–Nov).
Habitat Rocky sites, oak woodland Sandy soils, burned pinelands, turkey oak sand ridges, pine-oak and oak-hickory upland woods, old fields, roadsides, fencerows, moist sites
Elevation 1000–2200 m (3300–7200 ft) 100–900 m (300–3000 ft)
Distribution
from FNA
AZ; Mexico (Chihuahua, Durango, Jalisco, Sinaloa, Sonora)
[BONAP county map]
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]
Discussion

Ageratina thyrsiflora is known from the United States from a single collection dated 1929 from “near Nogales” in Santa Cruz County. It is recognized by its strict, unbranched or few-branched stems with alternate, densely arranged leaves, relatively small heads densely clustered in terminal aggregates, orange-veined phyllaries and corollas, and closely puberulent stems and petioles (hairs minute, sharply upwardly bent).

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

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.)
Source FNA vol. 21, p. 553. FNA vol. 21, p. 550.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratina Asteraceae > tribe Eupatorieae > Ageratina
Sibling taxa
A. adenophora, A. altissima, A. aromatica, A. havanensis, A. herbacea, A. jucunda, A. lemmonii, A. luciae-brauniae, A. occidentalis, A. paupercula, A. rothrockii, A. shastensis, A. wrightii
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
Synonyms Kyrstenia thyrsiflora Eupatorium aromaticum, Eupatorium latidens
Name authority (Greene) R. M. King & H. Robinson: Phytologia 19: 227. (1970) (Linnaeus) Spach: Hist. Nat. Vég. 10: 286. (1841)
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).



Type/paste one or more Latin names into the boxes above; matching taxa will show up below the box as you type. You can use the up/down arrow keys to move through the list.

(If the plant you're looking for doesn't show up in the auto-complete list, that means it either isn't described in Flora of North America yet, or it's listed under a synonym. And please note that Flora of North America is still missing several plant families, including Apiaceae, Boraginaceae, and Polemoniaceae.)

Choose a data source: Flora of North America

The species comparison tool is brought to you by:
Northwest Wildflowers