Glab. perennial herb with very stout deeply descending taproot. Flowering stem erect, up to c. 1 m. tall and 4 cm. diam. Lvs up to c. 6 dm. long, including sheathing petiole with 2 delicate blunt lobes. Lamina ± 15-30 × 10-20 cm. Primary pinnae 4-5 pairs, segs up to 8 cm. × 3 mm., linear, ± flaccid, bluntly mucronate. Infl. of several umbels, subpaniculately arranged, on stout peduncles c. 5-10-(15) cm. long. Primary bracts with broad base and pinnatisect lamina. Male umbels slender, with up to 15 rays ± 1 cm. long. Female umbels with 3-6 rays. Involucral bracts few, linear-lanceolate, acuminate. ♂ with distinct triangular acute calyx-teeth; petals oblong to ovate-oblong, ± 2 mm. long, inflexed. ♀ with distinct narrow-triangular, subacute calyx-teeth; petals c. 1·5 mm. long, obovate, inflexed. Fr. ± 15 × 10 mm., dorsally much-compressed. Mericarps, one 3- the other 2-(3)-winged; wings up to c. 3 mm. wide. Vittae 1-2 in each groove, 2-3 on commissural face.