Eupatorium

Contains 26 accepted taxa overall.

Characteristics
Eupatorium L.
ASTERACEAE
THOROUGHWORT
View specimens within this family
The genus Eutrochium is now commonly recognized and segregated from Eupatorium (Ito et al. 2000; Schmidt & Schilling 2000; Tippery et al. 2014).
Classification
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ASTERALES
Eupatorium
Citation
EUPATORIUM Linnaeus, Sp. Pl. 836. 1753.
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TYPE: Eupatorium cannabinum Linnaeus Lectotypified by Britton & A. Brown, Ill. Fl. N. U.S., ed. 2. 3: 355. 1913.
Species
Scientific Name Common Name Herbarium Specimens Status Photos
Eupatorium ×pinnatifidum
Eupatorium album White-bracted Thoroughwort
Eupatorium altissimum Tall Thoroughwort
Eupatorium anomalum Anomalous Eupatorium
Eupatorium capillifolium Common Dog-fennel, Yankeeweed
Eupatorium compositifolium Coastal Dog-fennel, Yankeeweed
Eupatorium cordigerum Clasping Roundleaf Eupatorium
Eupatorium fernaldii Vasey's Eupatorium
Eupatorium glaucescens Wedgeleaf Eupatorium, Broadleaf Bushy Eupatorium
Eupatorium hyssopifolium Hyssopleaf Eupatorium
Eupatorium leptophyllum Limesink Dog-fennel
Eupatorium leucolepis Savanna Eupatorium, Justiceweed
Eupatorium linearifolium Narrowleaf Bushy Eupatorium
Eupatorium mohrii Mohr's Eupatorium
Eupatorium paludicola Swamp Justiceweed
Eupatorium perfoliatum Boneset
Eupatorium pilosum Ragged Eupatorium
Eupatorium pubescens Inland Roundleaf Eupatorium
Eupatorium recurvans Recurved Eupatorium
Eupatorium resinosum Resinous Boneset, Pinebarren Eupatorium
Eupatorium rotundifolium Common Roundleaf Eupatorium
Eupatorium scabridum Roughleaf Eupatorium
Eupatorium semiserratum Smallflower Thoroughwort
Eupatorium serotinum Late Eupatorium
Eupatorium sessilifolium var. sessilifolium
Eupatorium torreyanum Torrey's Eupatorium
Identification Key
1.  Leaves pinnatifid, or pinnately or ternately lobed, lobes linear to linear-lanceolate, margins entire (Traganthes group)
Key A
1.  Leaves simple, not lobed, margins crenate, entire, laciniate, serrate, or serrulate (core Eupatorium group)
Key B
1.  (Key A) Leaf blades or lobes linear-lanceolate, to 4 mm wide; heads in subcorymbiform to subpaniculiform arrays; florets 7-9
E. x pinnatifidum
1.  Leaf blades or lobes usually linear and <3 mm wide; heads in paniculiform arrays; florets usually 5
2
2.  Stems glabrous; heads secund on branches
E. leptophyllum
2.  Stems puberulent; heads not secund on branches
3
3.  Leaf blades or lobes 0.2-0.5(1) mm wide (margins strongly revolute); phyllaries usually glabrate or glabrous, usually not gland-dotted
E. capillifolium
3.  Leaf blades or lobes 0.5-2.5(4) mm wide; phyllaries usually puberulent (mostly on midveins), usually gland-dotted
E. compositifolium
1.  (Key B) Petioles of larger leaves 5-30 mm long
2
1.  Petioles 0-5(10) mm long
3
2.  Leaf blades deltate to rhombic, to 6(8) cm long, coriaceous-subsucculent, margins generally crenate-undulate; florets 5
E. mikanioides
2.  Leaf blades lanceolate, to 15 cm long, chartaceous to membranaceous, margins mostly serrate to serrate-crenate; florets 9–15
E. serotinum
3.  Leaf bases connate-perfoliate
E. perfoliatum
3.  Leaf bases not connate-perfoliate
4
4.  Phyllaries with a white filiform to acuminate apex
5
4.  Phyllaries with an acute, obtuse, to rounded, green to white apex
7
5.  Leaves 4-10(15) mm wide, secondary veins weak or obscure
E. leucolepis
5.  Leaves (5)10-45 mm wide, secondary veins conspicuous throughout
6
6.  Leaves usually gland-dotted; phyllaries puberulent to villous (at least toward bases and on midveins), gland-dotted
E. album
6.  Leaves eglandular or sparsely gland-dotted; phyllaries glabrous, eglandular
E. petaloideum
7.  Leaf blades usually broadest below the middle, bases usually broadly cuneate, rounded, subcordate, or truncate
8
7.  Leaf blades usually broadest near or above the middle, bases cuneate to attenuate
9
8.  Leaf blades elliptic, lanceolate, or lance-ovate, mostly 1.6-2.5 times longer than wide; inflorescence branches alternate; phyllary glands nearly colorless
E. pilosum
8.  Leaf blades usually ovate to deltate, mostly 1-1.6(2) times longer than wide; proximal inflorescence branches often opposite to subopposite; phyllary glands yellow to golden
E. rotundifolium
9.  Leaves strongly 3-nerved from the base to near the apex
E. altissimum
9.  Leaves 1-nerved, pinninerved, or weakly 3-nerved
10
10.  Leaves usually in whorls of 3s or 4s, sometimes opposite, blades linear, (6)8-40 times longer than wide
11
10.  Leaves usually opposite, occasionally whorled, blades elliptic, lance-elliptic, lance-oblong, oblanceolate, or oblong, 2.5-16 times longer than wide
12
11.  Leaves 2-5 mm wide, margins usually entire to obscurely serrulate
E. hyssopifolium var. hyssopifolium
11.  Leaves 5-15 mm wide, margins usually laciniately toothed
E. hyssopifolium var. laciniatum
12.  Leaf blade upper surface glabrous or glabrate
13
12.  Leaf blade upper surface finely puberulent or villous
14
13.  Leaves usually recurved, the blades 2-8 cm long, 0.5-1(2) cm wide
E. mohrii
13.  Leaves usually spreading to ascending, the blades 15-50 cm long, (0.5)1–2 cm wide
E. anomalum
14.  Plant usually with some branches near the base; leaf blades mostly 2-3.5(4.5) cm long, margins weakly serrate to subentire; phyllaries lanceolate, larger ones 3-5 mm long; corollas 3-3.5 mm long
E. linearifolium
14.  Plant usually unbranched below the middle; leaf blades (3)5-7 cm long, margins usually serrate; phyllaries elliptic, larger ones 2.5-3 mm long; corollas 2.5-3 mm long
E. semiserratum
Genus Synonyms
Synonym Full Citation Basionym Type
No synonyms found.