Eupatorium linearifolium |
Eupatorium rotundifolium |
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waxy thoroughwort |
round-leaf boneset, round-leaf thoroughwort, roundleaf eupatorium |
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Habit | Perennials, 30–100+ cm. | Perennials, 40–100+ cm. | ||||||||
Stems | (from short caudices) single or multiple, branched at or near bases, pubescent throughout. |
(from short rhizomes) single, sparsely branched distally, puberulent. |
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Leaves | usually opposite (distal sometimes alternate); sessile or subsessile; blades 3-nerved distal to bases, oblong to lance-oblong, 20–45 × 5–10 mm, bases cuneate, margins entire or serrate (teeth mostly proximal), apices acute, faces finely puberulent, gland-dotted. |
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. |
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Florets | 5; corollas 3–3.5 mm. |
5; corollas 3–4 mm. |
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Phyllaries | 8–10 in 1–2 series, lanceolate (tapering toward apices), 2–5 × 0.5–1 mm, apices rounded to acute, abaxial faces puberulent, gland-dotted. |
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. |
in corymbiform arrays. |
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Cypselae | 2.5–3 mm; pappi of 30–40 bristles 3–5 mm. |
2–3 mm; pappi of 30–40 bristles 3.5–4 mm. |
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2n | = 20, 30, 40. |
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Eupatorium linearifolium |
Eupatorium rotundifolium |
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Phenology | Flowering Jul–Sep. | |||||||||
Habitat | Dry, sandy soils, pine and oak woods, old fields | |||||||||
Elevation | 20–100+ m (100–300+ ft) | |||||||||
Distribution |
AL; DE; FL; GA; MS; NC; SC; TX
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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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Discussion | Plants treated here as Eupatorium linearifolium were long treated under the name E. cuneifolium; the latter name was superfluous when published (K. N. Gandhi and R. D. Thomas 1991). Because there appears to be a continuous range of variation between diploids that were referred to by V. I. Sullivan (1972) as E. cuneifolium and the series of putative hybrids (with E. hyssopifolium suggested as the other parent) that she called E. linearifolium, these are combined here. The tendency for the plants to branch at or near the bases is distinctive within Eupatorium. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
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Key |
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Source | FNA vol. 21, p. 470. | FNA vol. 21, p. 472. | ||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Eupatorium | Asteraceae > tribe Eupatorieae > Eupatorium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | E. cuneifolium, E. glaucescens, E. tortifolium | |||||||||
Name authority | Walter: Fl. Carol., 199. (1788) | Linnaeus: Sp. Pl. 2: 837. (1753) | ||||||||
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