Us. very aromatic glab. herb; stems much-branched, creeping, rooting, ascending at tips, stout, c. 2-4 mm. diam.; plant forming close to rather open patches up to ± 1 m. diam.; branches stout, ringed by lf-scars. Lvs clustered on branchlets on rather fleshy petioles ± (10)-20-25 mm. long, prolonged into broad sheaths 10-30 mm. long. Lamina pinnate to pinnatisect, broad-oblong, 10-15-(40) × 4-15 mm. Pinnae us. 2 pairs below terminal 3-lobed apical portion, but sts more compound, coriac., ± fleshy, glab., opp., obliquely oblanceolate, acute to subacute, gland-dotted, up to 7 × 2 mm. Scape slender, ± 5-10 cm. long, sparsely to rather densely clad in ascending white hairs; bracts several to 1, distant, linear, up to ± 5 mm. long. Capitula (8)-10-15-(20) mm. diam.; receptacle convex. Phyll. in 2-3 series, ovate- to narrow-oblong, 4-5 mm. long, ± hairy on outer surface, glandular; margins purple, ± erose, scarious, sts apiculate, sts accrescent. Florets glandular, ♂ and ♀ us. on same plant, but plants sts dioec. ♀ with corolla cut above into 4 ovate-triangular teeth, ± 1 mm. long; ♂ funnelform, 3-6 mm. long; teeth 4, minute, triangular. Achenes compressed-obovoid, eglandular, to glandular, 2-3 mm. long, ribbed, ± muriculate.

2n = c. 156, 208

A creeping perennial herb forming ± discrete patches us. less than 1 m wide. Rhizomes on the soil surface or intertangled and lying on old decaying rhizomes, stout, 1-3 mm diam., dark and sparsely pilose, becoming woody and glabrous; branches us, clustered, up to 6 radiating from around a flowering node; leaves clustered at apex, but under better conditions older leaves up to 3 cm apart. No short shoots. Roots ± extensive and stout, up to 20 cm long and 1 mm diam. Leaves 1-pinnatifid, occ. simple, 0.5-4.0 × 0.3-1.0 cm (only ca. 1 mm wide if simple); blade 0.4-1.5 cm long, elliptic to obovate or broadly so, coriaceous, thick, dark green, glabrous, midrib not raised on ventral surface; pinnae 1-5 pairs, distant, cut to midrib, obovate, obtuse; teeth us. 0, occ. 1 on either side of larger pinnae, cut 1/3—½ across pinna, triangular. Peduncles longer than leaves, 2-12 cm, us. with 1-8 evenly spaced small linear bracts, occ. nude, sparsely pilose. Occ. monoecious, us. subdioecious with pistillate, staminate and bisexual heads common. Pistillate heads 0.5-1.5 cm diam.; surface flat or slightly convex; involucre hemispherical; phyllaries 20-110 in 2 or more subequal rows, oblong, dark green, with a single dark vein ± evident, glabrous, with wide brown scarious margin, not growing after anthesis; florets 50-300 in numerous rows, 2.75-4.0 mm long, straight, white; corolla 2-4 times as long as wide, with equal teeth. Staminate heads larger, 0.5-1.8 cm diam.; surface convex; involucre spreading or flat; phyllaries 10-60; florets us. fewer, 40-300, occ. with a dark stripe down the broader part of the corolla. Bisexual heads intermediate; in subdioecious populations with all possible percentages of pistillate and staminate florets; in monoecious populations with 15-60 pistillate florets surrounding 50-90 staminate florets. Achenes up to 2.3 × 1.0 mm. ± compressed, biconvex, golden-brown or dark brown, scarcely wrinkled. Flowers in summer.