Strongly aromatic, rhizomatous, perennial herb. Stems erect, 30-200 cm tall, ribbed, glabrous or sparsely clothed in short hairs and glandular hairs especially above, branched above to form infl. Basal lvs petiolate (but often with very reduced leaflets along sheath), ovate, elliptic, or obovate, glabrous to moderately clothed in short hairs and with often numerous pitted glandular hairs, 1-pinnate with leaflets again 1-pinnatisect, c. 15-25 × 5-10 cm; primary leaflets in c. 10-15 pairs, lanceolate to narrow-ovate, all in one plane, sessile; ultimate segments lanceolate to triangular, serrate. Cauline lvs similar to basal, but usually glabrous and densely glandular, above becoming sessile, smaller and with fewer, less divided leaflets. Corymb with (6)-15- numerous, densely packed capitula. Involucral bracts usually glabrous, rarely with a few scattered hairs, 2-5 mm long; margin brown, membranous, especially at apex. Capitula (6)-8-10-(12) mm diam.; outer florets ♀ but not or very shortly ligulate, yellow; disc florets numerous, yellow. Achenes c. 1.5 mm long, brown, glandular, ribbed; corona lobed, c. 0.2 mm long.