Eupatorium rotundifolium

Linnaeus

Sp. Pl. 2: 837. 1753.

Common names: Roundleaf thoroughwort
Endemic
Treatment appears in FNA Volume 21. Treatment on page 472. Mentioned on page 464, 466, 467, 468, 470, 471, 473.

Perennials, 40–100+ cm. Stems (from short rhizomes) single, sparsely branched distally, puberulent. 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, glanddotted. Heads in corymbiform arrays. Phyllaries 8–10 in 2–3 series, elliptic to oblanceolate, 2–6 × 0.5–1.5 mm, apices acute, abaxial faces puberulent, glanddotted. Florets 5; corollas 3–4 mm. Cypselae 2–3 mm; pappi of 30–40 bristles 3.5–4 mm.

Distribution

V21-1183-distribution-map.gif

Ala., Ark., Conn., D.C., Del., Fla., Ga., Ind., Ky., La., Mass., Md., Miss., Mo., N.C., N.H., N.J., N.Y., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va.

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.

Selected References

None.

Key

1 Leaf blades 3-nerved from bases, bases subtruncate to broadly cuneate, margins crenate Eupatorium rotundifolium var. rotundifolium
1 Leaf blades 3-nerved distal to bases, bases broadly cuneate to cuneate, margins serrate > 2
2 Leaf blades 30–70 × 30–60 mm, broadest nearmiddles Eupatorium rotundifolium var. ovatum
2 Leaf blades 20–50 × 15–30 mm, broadest nearbases Eupatorium rotundifolium var. scabridum

"fine" is not a number.

... more about "Eupatorium rotundifolium"
not tailed +, truncate +, rounded +  and obtuse +
acute;acute +
scarious +
usually ovate +  and lanceolate +
usually terete +  and clavate +
diffuse +  and dense +
indeterminate +  and determinate +
Kunsiri Chaw Siripun +  and Edward E. Schilling +
Linnaeus +
puberulent +
broadly rounded +  and truncate +
enlarged +
5 cm50 mm <br />0.05 m <br /> (7 cm70 mm <br />0.07 m <br />) +
4 cm40 mm <br />0.04 m <br /> (6 cm60 mm <br />0.06 m <br />) +
1.5 cm15 mm <br />0.015 m <br /> (5 cm50 mm <br />0.05 m <br />) +
dissected +, lobed +, toothed +  and entire +
ovate;less deltate;orbiculate +
1.5 cm15 mm <br />0.015 m <br /> (4 cm40 mm <br />0.04 m <br />) +
papillate +  and rugose +
(4-)5-angled;10-ribbed +
filiform +
0.35 cm3.5 mm <br />0.0035 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
Roundleaf thoroughwort +
pinkish +  and white +
0.3 cm3 mm <br />0.003 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
prismatic +
fertile +  and bisexual +
Ala. +, Ark. +, Conn. +, D.C. +, Del. +, Fla. +, Ga. +, Ind. +, Ky. +, La. +, Mass. +, Md. +, Miss. +, Mo. +, N.C. +, N.H. +, N.J. +, N.Y. +, Ohio +, Okla. +, Pa. +, R.I. +, S.C. +, Tenn. +, Tex. +, Va. +  and W.Va. +
puberulent +  and villous +
pistillate +, staminate +  and neuter +
winged +  and beaked +
dispersed +
in usually determinate , rarely indeterminate , arrays +  and singly +
indeterminate +
each +  and sessile +
0.1 cm1 mm <br />0.001 m <br /> (0.3 cm3 mm <br />0.003 m <br />) +
obconic;ellipsoid +
subsessile +  and sessile +
triangular +
crenate +  and serrate +
2-carpellate +
persistent +
nerved +  and 2-3-nerved +
0.2 cm2 mm <br />0.002 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
8 +  and 10 +
0.05 cm0.5 mm <br />5.0e-4 m <br /> (0.15 cm1.5 mm <br />0.0015 m <br />) +
bearing subulate enations +, hairy +  and bristly +
convex;flat +
exalbuminous +
puberulent +
appendaged +  and truncate +
hirsutulous +
papillate +
Compositae +
Eupatorium rotundifolium +
Eupatorium +
species +
campanulate +
toothed +  and entire +
40 cm400 mm <br />0.4 m <br /> (100 cm1,000 mm <br />1 m <br />) +
vine +, shrub +  and subshrub +