Oryza sativa Linnaeus subsp. rufipogon (Griffith) de Wet; O. sativa var. rufipogon (Griffith) G. Watt.

Perennial, aquatic, tufted or stoloniferous. Culms decumbent, rooting and tillering at nodes, sometimes floating, lower part spongy, 0.7–1.5 m or more tall. Leaf sheaths slightly inflated below, upper sheaths tight, glabrous, auricles conspicuous, glabrous or ciliate; leaf blades up to 40 × 1–2 cm, margins and midrib scabrid, apex acuminate; ligule up to 17 mm. Panicle spreading, 12–30 cm, eventually nodding; branches 1–5 at lowest node, longest 2.5–12 cm, axils bearded or glabrous. Spikelets oblong, 8–11 mm, length 2.7–4.5 times width, yellowish green with reddish apex, deciduous; sterile lemmas lanceolate, ca. 2.5 mm, apex acuminate; fertile lemma finely reticulate with scattered short glassy hairs, flanks slightly sulcate, keel stiffly ciliate, apex acuminate; awn 5–40 mm or more, stout, scaberulous. Anthers 4–6 mm. Caryopsis reddish brown, 5–7 mm. Fl. and fr. Apr–May and Oct–Nov. 2n = 24.

This is a member of the AA genome complex, which includes cultivated rice, of which it is a progenitor. Members of this group hybridize quite easily and have contributed to the development of rice cultivars. Oryza rufipogon is perennial, but the most important difference from cultivated rice is the possession of readily deciduous spikelets.

Riversides, ponds, streams, lotus ponds, rice fields, ditches, marshes; below 700 m. Guangdong, Guangxi, Hainan, Taiwan, Yunnan [Bangladesh, Cambodia, India, Indonesia, Malaysia, Myanmar, New Guinea, Sri Lanka, Philippines, Thailand, Vietnam; Australia (Queensland)].