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Photo is of parent taxon

common white snakeroot, eupatoire rugueuse, white snakeroot

white snakeroot

Habit Perennials, (30–)50–80(–120) cm (bases usually fibrous-rooted crowns, sometimes rhizomatous).
Stems

ascending to erect, sometimes semiscandent, puberulent (hairs minute, crisped).

Leaves

opposite;

petioles (5–)10–30(–50) mm;

blades usually deltate-ovate to ovate or broadly lanceolate, sometimes ovate-lanceolate, 4–11(–13) × 2.5–8(–9) cm, bases usually rounded to truncate or obtuse, sometimes cordate, margins coarsely and doubly incised-serrate, apices usually acuminate.

Peduncles

1–5 mm, puberulent.

Involucres

4–5 mm.

Corollas

white, lobes sparsely short-villous.

Phyllaries

3–5 mm, apices not cuspidate.

apices acute, abaxial faces glabrous or sparsely and finely villous.

Heads

clustered.

Cypselae

glabrous.

Ageratina altissima var. altissima

Ageratina altissima

Phenology Flowering Jul–Oct(–Nov).
Habitat Moist forests, cove forests
Elevation 10–800 m (0–2600 ft)
Distribution
from FNA
AL; AR; CT; DE; FL; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NY; OH; OK; PA; RI; SC; SD; TN; TX; VT; WI; WV; NB; NS; ON; QC; SK
[BONAP county map]
from FNA
AL; AR; CT; DE; FL; GA; IA; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; NC; ND; NE; NH; NJ; NY; OH; OK; PA; RI; SC; SD; TN; TX; VA; VT; WI; WV; NB; NS; ON; QC; SK
[WildflowerSearch map]
[BONAP county map]
Discussion

Plants with narrow leaves, generally in the southwest part of the range of Ageratina altissima, have been recognized as var. angustata and were so mapped by A. F. Clewell and J. W. Wooten (1971), who indicated that all var. angustata occurs west of the Mississippi River and that this taxon was completely congruent in distribution with var. altissima. The present treatment confirms the westward tendency toward size reduction and observes that narrow-leaved plants occur widely through the southeast United States (including Arkansas, Kentucky, Louisiana, North Carolina, Oklahoma, Tennessee, and Texas). The transition is gradual and the region of intergradation is wide. In Texas, where the leaves mostly are narrow, plants with broad, cordate leaves are scattered through the range.

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

Varieties 2 (2 in the flora).

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

Key
1. Phyllaries 3–5 mm, apices not cuspidate
var. altissima
1. Phyllaries 4–7 mm, apices cuspidate to acuminate
var. roanensis
Source FNA vol. 21, p. 549. FNA vol. 21, p. 549.
Parent taxa Asteraceae > tribe Eupatorieae > Ageratina > Ageratina altissima Asteraceae > tribe Eupatorieae > Ageratina
Sibling taxa
A. altissima var. roanensis
A. adenophora, A. aromatica, A. havanensis, A. herbacea, A. jucunda, A. lemmonii, A. luciae-brauniae, A. occidentalis, A. paupercula, A. rothrockii, A. shastensis, A. thyrsiflora, A. wrightii
Subordinate taxa
A. altissima var. altissima, A. altissima var. roanensis
Synonyms A. altissima var. angustata, Eupatorium rugosum, Eupatorium rugosum var. chlorolepis, Eupatorium rugosum var. tomentellum, Eupatorium urticifolium Ageratum altissimum
Name authority unknown (Linnaeus) R. M. King & H. Robinson: Phytologia 19: 212. (1970)
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