Description from Flora of China
Herbs perennial or annual. Rhizome shortly or long creeping. Stems often tufted. Leaves either all basal or also cauline; leaf sheath open on 1 side, apex often auriculate; leaf blade grasslike, terete, or scalelike. Inflorescences terminal, or pseudolateral when basal involucral bract seemingly a continuation of stem, usually many flowered; ultimate divisions dense heads, lax cymes, or 1-flowered. Bracteoles present or absent. Perianth segments 6, in 2 whorls, papery to hyaline. Stamens 3 or 6, attached to base of perianth segments; filaments filiform; anthers oblong or linear. Ovary 1- or 3-loculed; placentas 3, parietal, sometimes inconspicuously prominent but more frequently protruding and sometimes connate at middle; ovules numerous per locule. Style 1; stigmas twisted. Capsule 3-valved; valves usually bearing placentas at middle. Seeds ovoid or oblong, minute, sometimes appendaged; appendage caudate.
Several species of Juncus reported from China are not treated in this account, either because the present authors have not seen any Chinese specimens, or because the species are not sufficiently well known to be properly placed. They include the following: Juncus beringensis Buchenau, J. brachyspathus Maximowicz var. brachyspathus J. dulongjiongensis Novikov, J. grubovii Novikov, J. jaxarticus V. I. Kreczetowicz & Gontscharow, J. orchonicus Novikov, and J. soranthus Schrenk.
About 240 species: widely distributed in both hemispheres, most abundant in temperate and cold regions, rarely tropical; 76 species (27 endemic) in China.