Us. large plants up to c. 1 m. tall, forming dense tussocks. Lvs ∞, 3-pinnate, spreading, subglaucous; margins and midribs crenulate-serrulate; occ. plants may have some lvs 2-pinnate. Sheaths erect, whitish, fleshy except membr. margins, up to 15 × 5 cm.; stipules with petiolate bases c. 2 × 1 cm., unequal, 3-foliolate, outer segs up to 20 cm., inner to 6 cm., terminal to 25 cm. long, pungent; petiolar or ligular portion sts up to c. 4cm. long. Petioles up to c. 15 cm. × 1-2 mm., internodes up to c. 5 cm. long. Primary pinnae us. 1 pair, again pinnate, internodes c. 3 cm. long; secondary pinnae us. 1 pair, again pinnate, sts bearing accessory pinnules; final segs up to 25 cm. × 4 mm., concavo-convex, with long pungent points. Stems of male plants ridged, up to ± 8 dm. × 2 cm. including infl. up to c. 4 dm. long. Bracts. ∞; sheaths pale, membr., ridged, up to 4 × 1 cm., tapering to apex. stipules unequal, up to 3 cm. × 1 mm. Lamina 3-foliolate; lateral pair of lflts up to c. 9 cm. long; terminal lflt to 20-25 cm. × 3 mm., stiff, pungent, becoming strongly reflexed. Umbels on stout peduncles up to c. 6-10 cm. long, us. with lateral umbellules near base as well as at apex, up to c. 4 cm. diam. Umbellules crowded, forming heads ± 2 cm. diam; rays ∞, ± 10 mm. long. Stems of female plants up to ± 1 m. tall including infl. up to c. 6 dm. tall. Bract-sheaths thin, ribbed; lower c. 5 × 2 cm. stipules unequal, 4-8-(15) cm. long. Lamina of lower sheaths pinnate, with occ. accessory pinnules; petiole flat, ± 10 mm. long, internodes to 2 cm. long; pinnae 2 pairs; terminal lflt up to 15 cm. long, at length strongly reflexed. Umbels c. 8, on stout peduncles ± 5 cm. long bearing lateral umbellules near base; involucral bracts linear. Umbellules ± 10, c. 15 mm. diam., on short rays. Petals pale yellow. Fr. c. 6-8 mm. long; mericarps 4-3-winged. Vittae 2-3 per furrow, 4-6 commissural.