About

Acer japonicum 'Ō-isami' is a deciduous tree that typically reaches a height of 7 to 8 meters. It features robust, thick branches and twigs, supporting leaves that are 9 to 11 lobed and can grow up to 20 centimeters wide, characterized by tapered tips and deep notches. The young foliage emerges in a light yellow-green hue, transitioning to a deep green as the season progresses. In the fall, the leaves transform into vibrant shades of red, yellow, and scarlet. During spring, it produces subtle red-purple flowers, which may give way to winged, red fruits.

About the genus

Acer consists of deciduous trees or sizable shrubs featuring pairs of leaves that are frequently palmately lobed. These plants produce small flowers that give way to distinctive winged fruits. Numerous species display vibrant autumn foliage, while certain varieties also exhibit decorative stems.

Growing conditions

Sunlight

Full sun, Partial shade

Soil type

Clay, Sand, Loam

Soil pH

Acid, Alkaline, Neutral

Soil moisture

Moist but well-drained

Aspect

East-facing, North-facing, West-facing

Exposure

Sheltered

UK hardiness

H6

Plant details

Plant type

Trees

Habit

Bushy

Foliage

Deciduous

Height

4-8 metres

Spread

2.5-4 metres

Time to full height

10-20 years

Suggested uses

Cottage and informal garden, Wildlife gardens

Care notes

Cultivation

Grow in any moisture-retentive, well-drained soil in a sheltered position. Leaf colour is best in partial shade, although full sun can be tolerated if soil is reliably moist. Leaf scorch can be caused by lack of soil moisture or excessive exposure. See Japanese maples cultivation

Pruning

Very little to no pruning required. For more advice refer to pruning group 1.

Propagation

Propagate by layering in autumn, grafting in late winter or softwood cuttings

Pest resistance

May be susceptible to Acer gall mite, aphids, caterpillars and horse chestnut scale

Disease resistance

May be susceptible to Verticillium wilt, acer leaf scorch and honey fungus