Plants perennial, glabrous or indistinctly papillose exclusively on veins of leaf blades abaxially, with fusiform, vertical rootstock. Stems erect, branched from above middle or in distal 2/3, 70–150(–200) cm. Leaves: ocrea deciduous or partially persistent at maturity; blade broadly lanceolate to oblong-lanceolate, normally 15–25(–35) × 5–7(–12) cm, base truncate, rounded, or slightly cordate, margins entire, undulate or weakly crisped, occasionally flat, apex acute or acuminate. Inflorescences terminal, occupying distal 1/2–2/3 of stem, normally dense or interrupted near base, broadly paniculate (branches of inflorescence mostly with 2d-order branches), branches usually straight or arcuate, rarely indistinctly flexuous. Pedicels articulated near middle, filiform, 6–14 mm, articulation distinctly swollen. Flowers 15–20 in whorls; inner tepals orbiculate, 6–8(–9) × 6–7.5(–8) mm, base usually distinctly cordate, margins entire or subentire near apex, distinctly dentate in basal 1/2, apex acute or subacute, teeth 0.5–1 mm; tubercles normally 3, rarely 1, distinctly unequal. Achenes dark brown or brown, 2.8–3.5 × 2–2.5 mm. 2n = 80.
