Eupatorium rotundifolium |
Eupatorium anomalum |
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round-leaf boneset, round-leaf thoroughwort, roundleaf eupatorium |
Florida thoroughwort |
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Habit | Perennials, 40–100+ cm. | Perennials, 80–150+ cm. | ||||||||
Stems | (from short rhizomes) single, sparsely branched distally, puberulent. |
(from tuberous rhizomes) single, densely branched distally (shoots often develop from lateral buds), puberulent throughout (denser distally). |
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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. |
usually opposite (distal sometimes alternate); sessile or subsessile; blades 3-nerved distal to bases, elliptic to oblong, 15–50 × (5–)10–20 mm, bases cuneate, margins entire or serrate (unevenly toothed), apices rounded to acute, faces puberulent (abaxial) or glabrate (adaxial), gland-dotted (both). |
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Florets | 5; corollas 3–4 mm. |
5; corollas 3–3.5 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. |
8–12 in 2–3 series, oblong to lanceolate, 2.5–5 × 0.5–0.7 mm, apices rounded to acute, abaxial faces puberulent throughout. |
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Heads | in corymbiform arrays. |
in corymbiform arrays. |
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Cypselae | 2–3 mm; pappi of 30–40 bristles 3.5–4 mm. |
1.8–3 mm; pappi of 20–35 bristles 3.5–4.5 mm. |
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2n | = 20, 30, 40. |
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Eupatorium rotundifolium |
Eupatorium anomalum |
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Phenology | Flowering Jul–Aug. | |||||||||
Habitat | Wet, low ground, flatwoods | |||||||||
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; FL; GA; NC; SC |
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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.) |
Of conservation concern. Eupatorium anomalum has been proposed to be intermediate in morphology between E. rotundifolium and E. mohrii and, possibly, a hybrid derivative of that pairing. Molecular data suggest that its derivation is from hybridization between E. serotinum and E. mohrii. (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. 466. | ||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Eupatorium | Asteraceae > tribe Eupatorieae > Eupatorium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Name authority | Linnaeus: Sp. Pl. 2: 837. (1753) | Nash: Bull. Torrey Bot. Club 23: 106. (1896) | ||||||||
Web links |