Federal Noxious Weed Disseminules of the U.S.

Oryza punctata Kotschy ex Steudel

Family: Poaceae,  Tribe: Oryzeae

Common names:  red rice

Disseminule 

Fertile floret with two glume-like sterile lemmas; disarticulation above the glumes (below the sterile lemmas).

Description

Disseminule (floret with 2 sterile lemmas) elliptic to oblong, ca. 4.5–9.2 mm long, 1.9–2.6 mm wide; callus smooth; disarticulation scar centric or slightly eccentric. Sterile lemmas similar, glume-like, linear, glabrous, 1–2 mm long. Rachilla internode not pronounced below fertile lemma. Fertile lemma and palea strongly laterally compressed, keeled, cartilaginous, surface scaberulous and tuberculate in a grid pattern. Lemma 4.5–9.2 mm long, 5-nerved; its margins inrolled, interlocking palea margins; with apical awn 10–75 mm long, slender, straight, antrorsely barbed. Caryopsis lanceolate or oblong, 4–4.8 mm long, 1.5–1.8 mm wide, oblong, laterally compressed, reddish; hilum linear, as long as caryopsis.

Identification considerations

The wild red rices (O. longistaminata, O. punctata and O. rufipogon) can be distinguished from O. sativa L. (cultivated rice) by their red caryopses, although it may be difficult to differentiate the wild red caryopses from commercial rice cultivars with red grains.

Oryza punctata can be distinguished from O. rufipogon and O. longistaminata by its shorter fertile florets, rachilla not pronounced between the sterile lemmas, awns relatively slender and flexuous, and spikelets transversely (not obliquely) attached to pedicel.

Similar species

Oryza longistaminata A. Cheval. & Roehr.

Oryza rufipogon Griff.

Distribution

Native to tropical Africa, South Africa and Madagascar. Introduced into Thailand.

Habitat

Flooded watercourses, stream banks, pond margins, rice fields.

General information

Oryza punctata is a tufted annual grass, to 120 cm tall. See comments about the weediness of the wild red rices in the O. rufipogon fact sheet.