Flowering in April; fruiting in September.
Acer pectinatum subsp. pectinatum is close relative of Acer pectinatum subsp. taronense, but differs from the latter in its petioles glabrous (vs. pubescent), leaves usually 5-lobed (vs. 3-lobed), abaxially slightly pubescent on veins (vs. densely rufous pubescent on veins when young).
Acer pectinatum is occurring in S Xizang, NW Yunnan of China, Bhutan, NE India, NE Myanmar, Nepal.
Trees to 8 m tall. Bark dark brown, smooth. Branchlets purplish, glabrous; winter buds purplish. Leaves deciduous; petiole purplish red, 6-7 cm, glabrous; leaf blade suborbicular, 7-10 cm long, 6-8 cm wide, 5-lobed, abaxially pubescent especially on veins, adaxially glabrous, primary veins 5, lateral veins 8 or 9 pairs, base cordate, deeply cordate; middle lobe ovate, apex caudate-acuminate, acumen ca. 1 cm; lateral lobes triangular, margin serrate, apex caudate-acuminate. Inflorescence terminal on leafy branchlets, appearing after leaves develop, racemose, 6-8 cm, 10-40-flowered. Pedicel 5-7 mm, slender, glabrous. Staminate flowers: sepals 5, purplish green, oblong, ca. 5 mm, glabrous, apex obtuse; petals 5, obovate, apex obtuse; stamens 8, ca. 2 mm, glabrous; disk glabrous, intrastaminal; ovary rudimentary. Fruit yellowish; nutlets flat, ca. 7 mm long, 4 mm wide; wing falcate, including nutlet 1.6-2.5 cm long, 6-8 mm wide, wings spreading nearly horizontally.
The chromosomal number of Acer pectinatum is 2n = 26 (Mehra, 1976).
Growing in mixed forest; 2500-3700 m.
