Description from Flora of China
Cotoneaster koidzumii Hayata, J. Coll. Sci. Imp. Univ. Tokyo 30(1): 101. 1911; C. formosanus Hayata; C. taitoensis Hayata; Pyracantha formosana Kanehira; P. koidzumii var. taitoensis (Hayata) Masamune.
Shrubs caespitose. Branchlets dark gray, often thornlike, initially pubescent, glabrous when old. Leaves usually 3–5-fascicled; petioles ca. 3 mm, puberulous; leaf blade narrowly elliptic to narrowly obovate, 3–4.5 × 0.7–1.2 cm, abaxially glaucescent, densely pubescent when young, glabrescent, adaxially glabrous, base cuneate, margin entire, apex slightly emarginate or truncate. Corymb 3–4 cm in diam., many flowered; peduncle sparsely pubescent; bracts caducous, lanceolate. Pedicel 5–11 mm, sparsely pubescent. Flowers 8–10 mm in diam. Hypanthium campanulate, abaxially densely pubescent. Sepals triangular, 1–1.2 mm, abaxially densely pubescent when young, apex acute. Petals suborbicular or broadly elliptic, 3.5–4 × 3–4 mm, apex slightly emarginate. Stamens 20; filaments 2–3 mm. Ovary pubescent; styles nearly as long as stamens. Pome orangish red, depressed-globose, 4–5 mm. Fr. Aug–Nov.
Rocky valley areas, seashores, thickets, among shrubs. Taiwan.