Caespitose perennials forming colonies, compact hard rhizome covered with white soft tomentum of multicellular hairs. Leaves rosulate, linear-acuminate, up to 250 x 8 mm, but usually much smaller, apex acute, obtuse or drawn out into a long fine point. Capitula 1-3 per rosette on long thin peduncles, globose, c. 10 mm in diam., usually densely covered by a tomentum of hard, short, white setae; monoecious with male flowers predominating or some capitula entirely male; involucral bracts glabrous, usually reflexed, oblong, pale; floral bracts dark with white setae near apex; receptacle glabrous to villous. Female flower, sepals 3, black, boat shaped, 2-4 mm long, with a convex, occasionally toothed keel, apex acute, tufted with white setae, margin fimbriate; petals 3, spathulate, pale, densely setose and with a black gland; ovary 3-lobed. Male flower: sepals 3, dark, setose at apex; petals 3, unequal in size, white, setose above with a black gland; stamens 6, anthers black. Capsule 3-lobed; seeds smooth, testa with a rectangular network; ripe seeds rare.
Caespitose herb, hydrophyte, 55-170 mm high, forming colonies; rhizome compact, covered with white, multicellular hairs. Leaves rosulate, linear, up to 250 x 8 mm, apex obtuse, with a small hardened knob. Capitula globose, usually covered with hard white setae, with male flowers predominating or sometimes entirely male; involucral bracts glabrous, reflexed, oblong. Female flower: sepals 3, black, boot-shaped, with a convex or toothed keel, margins tufted with white hairs; petals 3, spathulate, densely setose, with black glands; ovary 3-lobed. Male flower: sepals 3, setose at apex; petals 3, unequal in size, white, setose above with black gland; stamens 6; anthers black. Flowering time Sept.-Apr. Fruit a trilobed capsule.