Strongly rhizomatous perennial. Culms terete, more or less hard (i.e. relatively difficult to compress), shining, yellow-green, 40–130 cm long, 0.6–2.5 mm diam.; striations 22–60; pith interrupted with irregular, more or less circular or longitudinally ellipsoidal gaps, occasionally continuous above. Leaves reduced to basal cataphylls (mucro plus sheath) 5–18 cm long, lax around the culm, abaxially golden brown to dark yellow-brown or dark red-brown at base, adaxially golden brown. Inflorescence 2–6 cm long, diffuse, with densely clustered flowers, 3–20 per cluster and 1–20 clusters per inflorescence; lowest inflorescence bract erect, culm-like, 6–21 cm long, exceeding inflorescence. Flowers subtended by 2 bracteoles. Tepals 6, acute to acuminate or mucronate, straw-brown, occasionally tinged red-brown; outer tepals 1.7–2.6 mm long, exceeding inner tepals, with very narrow hyaline margins; inner tepals with broad hyaline margins. Stamens 3, shorter than outer tepals; anthers 0.4–0.6 mm long, less than or equalling filament length. Capsule 3-locular, slightly shorter than to slightly exceeding outer tepals, ellipsoid, dark golden brown, obtuse, shortly apiculate. Seeds 0.4–0.5(–0.6) mm long.

Affinis J. gregifloro sed culmis flavovirentibus nitentioribusque, medulla culmi densiori, minus interrupta, lacunis plusminusve ellipsoideis, capsulis fuscantioribus, differt.