Perennial, tussocky from a short rhizome. Culms slender, erect, 30–70 cm, nodes bearded. Basal leaf sheaths persistent, densely and conspicuously silky hairy; leaf blades linear, flat or convolute, stiff, 10–50 × 0.1–1 cm, abaxial surface glabrous, adaxial surface sparsely to densely hairy, base narrow; ligule membranous, ca. 1 mm. Inflorescence digitate; racemes 2–4, 4–12 cm, narrowly ascending, rachis pilose, spikelets grouped on pedicels of varying length. Spikelets lanceolate, 5–6 mm, pale to dark brown, sometimes with transverse banding; glumes sharply acute to shortly awned; lower glume ovate; upper glume margins ciliate, occasionally winged; lower lemma with a small palea corresponding to a thin triangular basal patch on the lemma; upper lemma ovate-lanceolate, ca. 4 mm, smooth, with a rigid 2–3 mm awn-point. Anthers orange, ca. 3 mm. Fl. and fr. Feb–Aug. 2n = 18.

Alloteropsis semialata is a polymorphic species, and is unique among grasses in possessing leaf anatomy corresponding to both C₃ and C₄ photosynthetic types. These physiological variants correspond very approximately to the color variants recognized below, which have been raised to subspecific rank for that reason. However, other morphological characters that have been used to separate the subspecies in South Africa do not result in a division into two taxa in China, so the subspecies are not upheld here. Investigations in South Africa have shown var. eckloniana to be diploid (2n = 18), whereas var. semialata comprises a polyploid series from tetraploid to octoploid.

Hill slopes. Fujian, Guangdong, Guangxi, Hainan, Sichuan, Taiwan, Yunnan [Cambodia, India, Indonesia, Laos, Malaysia, Thailand, Vietnam; Africa, Pacific Islands].