Eupatorium rotundifolium |
Eupatorium rotundifolium var. scabridum |
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round-leaf boneset, round-leaf thoroughwort, roundleaf eupatorium |
roundleaf thoroughwort |
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Habit | Perennials, 40–100+ cm. | |||||||||
Stems | (from short rhizomes) single, sparsely branched distally, puberulent. |
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Leaves | usually opposite (distal sometimes alternate, lateral buds dormant or producing 1 pair of leaves); sessile or subsessile; blades ± 3-nerved, usually ± deltate to orbiculate, sometimes ovate, 15–50(–70) × 15–40(–60) mm (lengths mostly 1–2 times widths), bases broadly rounded to truncate, margins crenate to serrate, apices acute, faces puberulent to villous, gland-dotted. |
blades 3-nerved distal to bases, 20–50 × 15–30 mm, broadest near bases, bases broadly cuneate to cuneate, margins serrate. |
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Florets | 5; corollas 3–4 mm. |
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Phyllaries | 8–10 in 2–3 series, elliptic to oblanceolate, 2–6 × 0.5–1.5 mm, apices acute, abaxial faces puberulent, gland-dotted. |
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Heads | in corymbiform arrays. |
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Cypselae | 2–3 mm; pappi of 30–40 bristles 3.5–4 mm. |
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2n | = 20, 30. |
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Eupatorium rotundifolium |
Eupatorium rotundifolium var. scabridum |
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Phenology | Flowering Jul–Aug. | |||||||||
Habitat | Disturbed sites | |||||||||
Elevation | 10–100+ m (0–300+ ft) | |||||||||
Distribution |
AL; AR; CT; DC; DE; FL; GA; IN; KY; LA; MA; MD; MO; MS; NC; NH; NJ; NY; OH; OK; PA; RI; SC; TN; TX; VA; WV
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AL; AR; FL; GA; LA; MO; MS; OK; SC; TX |
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Discussion | Varieties 3 (3 in the flora). Eupatorium rotundifolium is one of the more variable species of the genus; its apparent propensity to hybridize with other species has led it to be described as a compilospecies and has complicated its delimitation. Hybrids with E. perfoliatum and E. sessilifolium are sufficiently distinctive to be treated here as distinctive entities (E. ×cordigerum and E. godfreyanum, respectively), and the varieties ovatum and scabridum have also been proposed to be of hybrid origin. The boundaries between varieties are indistinct and individual specimens may be difficult to place with confidence. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Variety scabridum includes apomictic polyploids and has been suggested to have been derived from hybridization between var. rotundifolium and Eupatorium semiserratum. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 472. | FNA vol. 21, p. 473. | ||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Eupatorium | Asteraceae > tribe Eupatorieae > Eupatorium > Eupatorium rotundifolium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | E. scabridum | |||||||||
Name authority | Linnaeus: Sp. Pl. 2: 837. (1753) | (Elliott) A. Gray: in A. Gray et al., Syn. Fl. N. Amer. 1(2): 99. (1884) | ||||||||
Web links |