Perennials. Roots long, rarely short, ± fleshy. Rhizomes stout, rarely slender, fleshy, sometimes short but conspicuous. Stems branching sympodially, with 1 to few basal rosettes and 1 to few flowering stems. Stems sheathed basally by black membranous remnants of old leaf bases. Base of basal leaves long connate. Seeds coated with a membranous lamella forming spongy, complex hexagonal pits.

Nineteen species: North America, Asia, Europe; 17 species in China.