Flora of North America species comparison

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Ageratina shastensis

Ageratina herbacea

Mt. Shasta snakeroot, Shasta ageratina, Shasta snakeroot

desert ageratina, fragrant snakeroot, white thoroughwort
Habit Perennials, 15–45 cm (bases woody, enlarged, occasionally rhizomatous). Perennials or subshrubs, (20–)30–60(–80) cm (woody crowns and woody rhizomes).
Stems

erect (clustered from bases), puberulent to pubescent (often with some glandular hairs distally).

erect (brittle), minutely puberulent.
Leaves

opposite proximally, alternate on at least distal 1/2 of stems;

petioles 4–6 mm;

blades (venation raised-reticulate) orbiculate (juvenile) or deltate-ovate, 1.5–3 × 1–2 cm, (subcoriaceous) bases obtuse to truncate, margins entire or coarsely serrate to dentate, apices acute to acuminate, abaxial faces ± gland-dotted and/or stipitate-glandular.

opposite;

petioles 10–25 mm;

blades triangular to lanceolate-ovate or ovate, 2–5(–7) × 1.5–3.5(–4.5) cm, bases truncate to shallowly cordate, margins dentate to serrate-dentate, abaxial faces sparsely hispidulous to glabrate, eglandular.
Peduncles

(0–)2–15 mm, puberulent and stipitate-glandular.

4–15 mm, puberulent.
Involucres

10–11 mm.

4–5 mm.
Corollas

white, glabrous.

white, glabrous.
Phyllaries

apices acute, abaxial faces sparsely puberulent.

apices acute, abaxial faces granular-puberulent.
Heads

mostly borne singly (each often subtended by a leaflike bract).

clustered.
Cypselae

hispidulous.

finely strigose-hispidulous.
2n

= 34.

= 34.

Ageratina shastensis

Ageratina herbacea
Phenology Flowering Jun–Oct. Flowering (Jul–)Aug–Oct.
Habitat Cracks and crevices of nearly vertical limestone cliffs Pine, pine-oak, juniper, and pinyon-juniper woodlands, rocks along streams, slopes, ridges, washes
Elevation 400–1800 m (1300–5900 ft) 1400–2700(–2900) m (4600–8900(–9500) ft)
Distribution
from FNA
CA
[BONAP county map]
from FNA
AZ; CA; CO; NM; NV; TX; UT; Mexico (Baja California, Chihuahua, Coahuila, Sonora)
[WildflowerSearch map]
[BONAP county map]
Discussion

Ageratina shastensis is recognized by relatively large solitary heads and coarsely serrate, subcoriaceous leaves alternate on distal parts of stems.

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

Ageratina herbacea is recognized by the distinctive color of its usually yellow-green, sometimes grayish, leaves, granular-puberulent involucres (with minute, thickened, eglandular hairs), and woody rhizomes.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 21, p. 552. FNA vol. 21, p. 551.
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. thyrsiflora, A. wrightii
A. adenophora, A. altissima, A. aromatica, A. havanensis, A. jucunda, A. lemmonii, A. luciae-brauniae, A. occidentalis, A. paupercula, A. rothrockii, A. shastensis, A. thyrsiflora, A. wrightii
Synonyms Eupatorium shastense Eupatorium ageratifolium var. herbaceum, Eupatorium herbaceum
Name authority (D. W. Taylor & Stebbins) R. M. King & H. Robinson: Phytologia 45: 464. (1980) (A. Gray) R. M. King & H. Robinson: Phytologia 19: 222. (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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