Description from Flora of China
Acer grosseri Pax var. forrestii (Diels) Handel-Mazzetti; A. maximowiczii Pax var. minus W. W. Smith ex H. Léveillé; A. pectinatum Wallich ex G. Nicholson subsp. forrestii (Diels) A. E. Murray; A. pectinatum f. rufinerve A. E. Murray.
Trees to 17 m tall, andromonoecious. Bark rough. Branchlets slender, glabrous; winter buds purple, ellipsoid, small, glabrous. Leaves deciduous; petiole 2.5-5 cm, slender, glabrous or pubescent; leaf blade ovate, 7-12 × 5-9 cm, papery, abaxially glaucescent, rarely with barbed hairs at axils of reticulate veins, adaxially glabrous, base cordate or subcordate, margin doubly serrulate with adpressed acute teeth, 3-lobed or not; middle lobe triangular-ovate, apex caudate-acuminate; lateral lobes triangular-ovate, ca. 1/2 as long as middle lobe, apex acuminate. Inflorescence terminal on leafy branchlets, racemose, glabrous, 5-20-flowered. Pedicel 6-8 mm, slender, glabrous. Sepals 5, oblong, 3-4 mm, glabrous. Petals 5, obovate, 3-4 mm. Stamens 8, ca. as long as petals. Disk intrastaminal, glabrous. Ovary glabrous. Nutlets flat, ca. 7 mm in diam.; wing including nutlet 2.3-2.5 cm × ca. 8 mm, wings spreading obtusely. Fl. May, fr. Sep.
● Mixed forests, valleys; 3000-3800 m. SW Sichuan, NW Yunnan.