Eupatorium album |
Eupatorium ×pinnatifidum |
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white thoroughwort |
thoroughwort |
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Habit | Perennials, 40–100+ cm. | Perennials, 40–100+ cm. | ||||||||
Stems | (from short caudices or stout rhizomes) single, sparsely branched distally, pubescent throughout. |
(from short caudices) single, densely branched distally, puberulent 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. |
opposite (proximal) or alternate (nodes often appearing leafy, lateral buds develop leaves without axis elongation); sessile; blades (usually 1–2-pinnately or ternately lobed) or lobes pinnately nerved or 1-nerved, linear, 20–100 × 0.5–1.5 mm, bases narrowly cuneate to attenuate, margins entire or serrate, apices acute, faces puberulent, gland-dotted. |
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Florets | (4–)5; corollas 4–4.5 mm. |
7–9; corollas 2–2.5 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. |
10–12 in 2–3 series, elliptic to oblong, 1–3.5 × 0.5–1 mm, apices acute to acuminate, shortly mucronate, abaxial faces puberulent, gland-dotted. |
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Heads | in corymbiform arrays. |
in subcorymbiform to subpaniculiform arrays. |
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Cypselae | 2.5–3.5 mm; pappi of 40–50 bristles 3.5–4.5 mm. |
1–1.5 mm; pappi of 20–30 bristles 2.5–3 mm. |
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2n | = 20. |
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Eupatorium album |
Eupatorium ×pinnatifidum |
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Phenology | Flowering Aug–Oct. | |||||||||
Habitat | Dry to wet areas, roadsides, around ponds, open pine woods | |||||||||
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; FL; LA; MS; SC; TX; VA |
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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 ×pinnatifidum has been suggested to represent a series of recurrent hybrids between E. capillifolium or E. compositifolium and E. perfoliatum; molecular data, in addition to confirming that this combination occurs, also show that E. serotinum rather than E. perfoliatum is the second parent in at least some plants included in E. ×pinnatifidum. (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. 472. | ||||||||
Parent taxa | Asteraceae > tribe Eupatorieae > Eupatorium | Asteraceae > tribe Eupatorieae > Eupatorium | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | E. eugenei, E. pectinatum | |||||||||
Name authority | Linnaeus: Mant. Pl., 111. (1767): Syst. Nat. ed. 12, 2: 536. (1767) | Elliott: Sketch Bot. S. Carolina 2: 295. (1823) | ||||||||
Web links |