Shrubby bamboos. Rhizomes leptomorph, with running underground stems. Culms pluricaespitose, nodding; internodes usually terete, usually with a dense, persistent, apical, yellow-brown tomentose to setaceous ring below nodes, rarely apically glabrous; wall thick; nodes usually flat, sometimes prominent. Branches usually solitary, nearly as thick as culms. Culm sheaths persistent, usually shorter than internodes, papery or nearly leathery; auricles usually developed; blade usually recurved, lanceolate. Leaf sheaths cylindrical, very thick, smooth. Leaves usually large relative to culm size, transverse veins distinct. Inflorescence largely ebracteate, terminal, a raceme or open panicle; branches usually subtended by tiny bracts. Spikelets several to many flowered, pedicellate. Rachilla articulate. Glumes 2 or 3, ovate or lanceolate; lemma oblong or lanceolate, nearly leathery; palea 2-keeled, shorter than lemma; lodicules 3. Stamens 3, long exserted; anthers yellow. Ovary ovoid; style 1, short; stigmas usually 2 (3 in I. wilsonii), plumose. Caryopsis dark brown at maturity. 2n = 48.