Perennials, rhizomatous herbs or with a short aerial woody stem covered in compacted leaf bases. Leaves in a basal or terminal rosette, tristichously arranged, linear and sheathing at the base, without a ligule between the blade and the sheath; blade heterobifacial, flat or V-shaped in transverse section, the margins usually (and the keel sometimes) serrulate. Inflorescence either one or several ±globose heads subtended by several leaf-like bracts on a triangular or quadrangular peduncle or a highly branched panicle; if branching, each branch subtended by a bract that consists of a closed somewhat funnel-shaped base and an elongate to linear to triangular blade. Individual flowers inconspicuous, bisexual, actinomorphic; tepals 6 in total, free, equal or subequal, ±coriaceous or mambranaceous. Stamens 6, anthers basifixed, dehiscence longitudinal or lateral. Ovary superior, trilocular, with one or numerous ovules per locule. Style very short or absent, stigmas three. Fruit a loculicidal capsule.