<Korea Flora>

Deciduous tree with glabrous branches. Winter buds terminal 1 and opposite, acute with 6-10 scales. Terminal 5-8mm, longer than the later buds, leaf scars V shate. Leaves mostly rather shallowly 6- to 9-lobed, cordate to somewhat round at base, usually hairy on side, the lobes deltoid, entire or with few coarse teeth, acuminate and awn-tipped, 5 x 8 cm, the petioles 4-12 cm long; Inflorescence on short peduncles, corymbose, andromonoecious; flowers yellowish green, small, male flower 8-9 mm across and female flowers 1 cm long with rudimentary stames and 2mm 2 styles, sepals oblong and petals broadly oblanceolate; Wings and nutlet glabrous or short-pubescent while young, nearly erect to ascending, 4.0-4.5 cm. long, seeds 2-3cm × 1.5-1.8cm. 

Flowering Apri to May
Fruting mid Sept to mid Oct.
Distribution NE China, far eastern Russia, Kurils, Japan (Hokkaido to Kyushu); all over the peninsula

Ecological characteristics: It is shade tolerant under other trees when young, and is distributed from mountain valleys to mountain ridges, but mainly grows in places where there is humid, and its roots grow shallow, and the growth is somewhat slow. The tree suckers and sprouts and the germination rate are relatively good, and it is vunerable to air pollution in urban areas. Although Acer okamotoanum Nakai is considered a distinct species due to its large fruit and wings, which are both larger than those of A. okamotoanum and A. pictum. However, there is overlapping variation with A. pictum and A. okamotoanum in the Korean Peninsula and Japan, and A. okamotoanum is treated here as a synonym of Acer pictum. The presence of hairs on the back of the leaves is considered a characteristic of A. pictum var. pictum and forms without hairs on the back of the leaves are treated as A. pictum var. mono. A. pictum var. pictum is mainly distributed from northern Hokkaido to Kyushu in Japan, and is mostly found in the southern region of the Korean Peninsula, although it is sometimes also found in central regions. Other than the presence of hairs, there are no significant differences between var. pictum and var. mono.

Deciduous broadleaf tree. Hairs present on the underside of the leaves. leaf size 6-8cm × 8-12cm, and petiole 3-9cm long.

Distributed in southern Hokkaido, Japan to Kyushu; Korea nationwide.

Ohwi 1985 Flora of Japan

Tree, usually with glabrous branches; leaves depressed-orbicular, 7-15 cm. wide, deeply to rather shallowly 5- to 7-lobed, cordate to somewhat truncate at base, usually glabrous on upper side, short-pubescent to glabrous except for the axillary tufts of hairs beneath, the lobes deltoid to lanceolate, entire or with few coarse teeth, acuminate and awn-tipped, the petioles 4-12 cm. long, glabrous to short-pubescent; inflorescence on short peduncles, corymbose, 4-6 cm. across; flowers yellowish green, small, 5-7 mm. across; sepals oblong; petals broadly oblanceolate; samaras glabrous or short-pubescent while young, nearly erect to ascending, 2-3 cm. long inclusive of the wing. Apr.-May.  Mountains; Hokkaido, Honshu, Shikoku, Kyushu; rather common and very variable. Korea, Manchuria, Amur, Sakhalin, and China.

var. mayrii (Schwerin) Koidz. ex Nemoto (synonym)

Bark smooth; leaves reddish while young, depressed reniform-orbicular, shallowly 5-lobed, glabrous, the lobes short, broad; flowers larger; samaras often erect. Hokkaido, Honshu (n. distr.).