Tufted annual. Stems to 40 cm high, very slender in small plants but more rigid in larger ones, 3-angled, very leafy at base. Leaves < stems, to 2.5 mm wide, margins smooth except near tip. Involucral bracts 2-3, very widely spreading, unequal, at least the lowest >, to very much > inflorescence. Inflorescence a single head or small umbel with few very short rays. Spikelets in ovoid dark clusters, oblong or oblong-lanceolate, 4-8 × 2 mm, much compressed. Glumes not closely imbricate, ± 2 mm long, ovate, obtuse, with broad green keel and dark red-purple patch at tip and purple band inside the green margin. Stamens 3 or 2. Style-branches 2. Nut ± ½ length of glume, orbicular-obovoid, biconvex, black.