Tufted, up to 6 dm. tall; taproot stout; lvs 2-3-pinnate up to 25-(50) cm. long, margins thickened, apex with spinulose process ± 2 mm. long. Sheaths membr., 7-10 × 1-2 cm., gradually tapering to 1-2-pinnate stipules up to c. 4 cm. long with linear pungent segs; petioles c. 3 cm. long, lowest internodes c. 2 cm. long. Primary pinnae 4-5-(8) pairs, ± 8-12 cm. × 4-5 mm.; secondary pinnae 4-6-(8) pairs, 1-3 cm. long, irregularly cut to middle into acicular segs, or again pinnately divided. Stems of male and female plants similar, up to 6 dm. × 2.5 cm., deeply grooved; infl. broad-oblong, up to 30 cm. long, densely fld. Bracts ∞, lower verticillate; sheaths ± 3 cm. long; stipules spinulose, up to 15 mm. long; lamina (1)-2-3-pinnate, lower ± 6 cm. long. Umbels up to ± 5 cm. diam., compact, sts polygamous, ± exceeded by sheaths; involucral bracts linear-lanceolate. Fr. c. 8 mm. long; mericarps with 5-(4) narrow wings.