Eupatorium rotundifolium |
Eupatorium resinosum |
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round-leaf boneset, round-leaf thoroughwort, roundleaf eupatorium |
pine barren thoroughwort |
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Habit | Perennials, 40–100+ cm. | Perennials, 40–100+ cm. | ||||||||
Stems | (from short rhizomes) single, sparsely branched distally, puberulent. |
(from short rhizomes) single, branched distally (among heads), puberulent throughout. |
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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; blades pinnately nerved, narrowly elliptic, 40–100+ × 5–20 mm, bases cuneate (not perfoliate), margins serrate, apices acute to acuminate, faces puberulent, gland-dotted. |
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Florets | 5; corollas 3–4 mm. |
9–14; 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. |
10–12 in 2–3 series, elliptic to oblong, 1.5–4 × 0.8–1 mm, apices broadly acute to acute, abaxial faces puberulent, gland-dotted. |
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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. |
2–3 mm; pappi of 20–30 bristles 3–3.5 mm. |
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2n | = 20. |
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Eupatorium rotundifolium |
Eupatorium resinosum |
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Phenology | Flowering Aug–Sep. | |||||||||
Habitat | Moist, low ground, pocosins, bogs, cutover woodlands, pine barrens, acid soils | |||||||||
Elevation | 20–100+ m (100–300+ 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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NC; NJ; 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.) |
Eupatorium resinosum is in the Center for Plant Conservation’s National Collection of Endangered Plants. (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. 472. | ||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Eupatorium | Asteraceae > tribe Eupatorieae > Eupatorium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Name authority | Linnaeus: Sp. Pl. 2: 837. (1753) | Torrey ex de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 176. (1836) | ||||||||
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