Perennial, 10-30 cm. Rhizome with long stolons. Stem 1-1.5 mm diam., terete to subterete, deeply grooved, smooth or finely papillose, basal part often ascending with 1-2 nodes in loer parts of stem. Leaves basal, but 1-2 reduced cauline blades present; sheaths up to 50 mm, soft, cauline shaeths slightly inflated, mouth oblique; blades up to 10 cm long, up to 2 mm wide, smooth, unifacial or upper surface a narrow groove. Inflorescence a head with numerous tightly overlapping glumes; finally 25-35 mm diam., globose, sometimes wider than high; glumes 2.5-3.5 mm, narrowly triangular, acute, lowest 1-2 (-5) mm, widely clasping, obtuse, midnerve not reaching apex, blackish to dark brownish grey, margins widely scarious. Perianth bristles finally up to 25 mm long, white to yellowish white, smooth: stigmas 3(-4); anther c. 0.8 mm. Nut 1.7-2 x 0.5-0.7 mm, narrowly obovoid, compressed trigonous, often slightly curved, brown to dark brown, almost smooth, mat.