Rhodora 47: 192. 1945.
Perennials, 40–100+ cm. Stems (from short rhizomes) single, branched distally, densely pilose. Leaves usually opposite (distal sometimes alternate); sessile; blades ± 3-nerved or pinnately nerved, ovate, 3–9.8 × 1.6–5.7 cm, bases clasping or narrowly perfoliate, margins serrate, apices acute, faces (rugose) sparsely pilose (adaxial) or densely pilose (abaxial) and densely glanddotted. Heads in corymbiform arrays. Phyllaries 7–10 in 2–3 series, 4–12 × 1–4 mm, apices (usually white) acuminate to acute, abaxial faces pilose, glanddotted. Florets 5–8; corollas 2.5–3 mm. Cypselae 2–3 mm; pappi of 30–40 bristles 3.5–4.5 mm. 2n = 30, 40.
Phenology: Flowering Jul–Aug.
Habitat: Margins of woods, moist areas
Elevation: 10–100+ m
Ark., Miss., N.J., N.C., S.C., Va.
Eupatorium ×cordigerum is an apomictic, polyploid hybrid of E. rotundifolium and E. perfoliatum that occurs in disturbed areas where those two species occur together. It is not uncommonly encountered; it is unclear how long it persists.
"fine" is not a number.