Eupatorium album |
Eupatorium pilosum |
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white thoroughwort |
ragged thoroughwort, rough boneset |
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Habit | Perennials, 40–100+ cm. | Perennials, 30–100+ cm. | ||||||||
Stems | (from short caudices or stout rhizomes) single, sparsely branched distally, pubescent throughout. |
(from short rhizomes) single, sparsely branched distally, densely puberulent to pilose throughout. |
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Leaves | usually opposite (distal sometimes alternate); sessile; blades ± 3-nerved or pinnately nerved, elliptic to oblanceolate, 30–120 × 10–40 mm (lengths mostly 3–4 times widths), bases narrowly cuneate (sometimes oblique), margins subentire, serrate, or serrulate, apices rounded to acute, faces setulose (denser on midribs and veinlets) to glabrate, usually gland-dotted. |
usually opposite (distal sometimes alternate); simple, sessile or subsessile; blades ± 3-nerved (distal to bases), elliptic, lanceolate, or lance-ovate, 30–90 × 20–45 mm (lengths mostly 2–2.5 times widths), bases rounded to rounded-cuneate, margins unevenly serrate, apices acute to attenuate, faces puberulent, gland-dotted. |
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Florets | (4–)5; corollas 4–4.5 mm. |
5; corollas 3.5–4 mm. |
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Phyllaries | 9–15 in 2–4 series, linear, 1.5–9 × 0.6–1 mm, apices acuminate to attenuate, sometimes mucronate, abaxial faces pubescent throughout, gland-dotted. |
7–10 in 2–3 series, oblong to lance-oblong, 2–7 × 1–1.5 mm, apices (sometimes whitish) acuminate to acute, mucronate, abaxial faces puberulent, gland-dotted. |
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Heads | in corymbiform arrays. |
in corymbiform arrays. |
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Cypselae | 2.5–3.5 mm; pappi of 40–50 bristles 3.5–4.5 mm. |
3–4 mm; pappi of 30–50 bristles 4–5 mm. |
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2n | = 20, 30, 40. |
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Eupatorium album |
Eupatorium pilosum |
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Phenology | Flowering Jul–Sep. | |||||||||
Habitat | Moist, low ground, margins of ponds, sandy soils, savannas, ditches | |||||||||
Elevation | 20–100+ m (100–300+ ft) | |||||||||
Distribution |
AL; CT; DC; DE; FL; GA; KY; LA; MD; MS; NC; NJ; NY; OH; PA; SC; TN; VA; WV
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AL; CT; DE; FL; GA; KY; LA; MA; MD; MS; NC; NJ; NY; PA; RI; SC; TN; VA; WV
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Discussion | Varieties 3 (3 in the flora). Eupatorium album is represented by widespread diploid populations and by polyploid, apomictic populations, segregated as varieties, that may have arisen by hybridization with other species. Molecular data suggest that var. vaseyi arose via hybridization between var. album and E. sessilifolium. They also suggest that E. album var. subvenosum arose from hybridization between E. album var. album and E. serotinum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Eupatorium pilosum has been most commonly treated as a variety of E. rotundifolium; it is distinct morphologically by its leaves, which are narrower and 3-nerved distal to bases, rather than 3-nerved from bases. Distal leaves of E. pilosum tend to differ from the proximal by being alternate with entire margins. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 465. | FNA vol. 21, p. 471. | ||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Eupatorium | Asteraceae > tribe Eupatorieae > Eupatorium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | E. rotundifolium var. saundersii, E. verbenifolium | |||||||||
Name authority | Linnaeus: Mant. Pl., 111. (1767): Syst. Nat. ed. 12, 2: 536. (1767) | Walter: Fl. Carol., 199. (1788) | ||||||||
Web links |