Erect perennial herb, up to 3 m tall. Stems densely clothed in short eglandular hairs above, becoming almost glabrous below, tinged purple at least around nodes, branched above. Lvs in whorls of 3-4-(5); petiole glabrous to sparsely hairy, 15-35 mm long; lamina almost glabrous on upper surface, with sessile glands and hairy especially on veins on lower surface, ovate-lanceolate, acute to acuminate, serrate, 80-150 × 20-60 mm; uppermost lvs smaller. Capitula 2-5 mm diam., numerous in slightly convex terminal corymbs. Involucral bracts very unequal; inner bracts elliptic-oblong, sparsely ciliate but otherwise glabrous, 7-8 mm long; outer bracts sparsely hairy, from c. 1 mm long. Florets pink to purple. Achenes narrow-obpyramidal, brownish black, 4-5 mm long.