Acer palmatum Seeds | Japanese Maple

Japanese maple with deeply lobed leaves turning scarlet — Japanese maple (*Acer palmatum*): Sapindaceae, native to East Asia.

LATIN NAME: Acer palmatum

COMMON NAME: Japanese Maple

Plant Profile

Acer palmatum is a small deciduous tree of Japan, Korea and central China, rarely more than ten metres tall, with five- to nine-lobed leaves that turn scarlet, orange or purple in autumn. The species in the wild is variable, and centuries of selection have produced more than a thousand named cultivars.

The wild tree grows in the understorey of mountain forest, which is why it tolerates shade when young and why it prefers cool, moist, well-drained soil. The flowers are small and reddish in spring, and the fruit is a pair of winged samaras that spin as they fall. The bark is smooth and greenish on young wood, becoming grey and furrowed with age.

Science & Biotechnology

Autumn colour comes from anthocyanins, which are synthesised in the leaf as chlorophyll breaks down and the sugars trapped in the tissue are converted. A warm, sunny autumn with cool nights gives the strongest colour, and a wet, windy autumn strips the leaves before the pigments develop.

The cultivar range rests on a few genetic switches. Dissectum types have deeply divided leaves; variegatum types carry a virus-like chimera that produces white or pink patches, and it must be propagated from the variegated shoot or it reverts. Most cultivars are grafted, since seed gives unpredictable colour and habit. Most garden plants are sold as grafted two-year-olds, and the graft union should sit just above soil level, since burying it invites rot and suckering from the rootstock.

Uses & Benefits

The tree is grown for ornament, in gardens, in pots and as bonsai. The leaf is also used in Japanese sweets, where it is salted and pressed, and the wood is used for small turned objects and for decorative boxes.

In cultivation, the tree’s reputation for difficulty comes mostly from wrong siting. It scorches in hot sun and drying wind, and it suffers from verticillium wilt in soil that has grown tomatoes or potatoes. Given shade from the afternoon sun and a mulch, it is long-lived and nearly trouble-free. Seedlings are also used as rootstock for named cultivars, since the species germinates reliably and grows fast enough to graft in two years.

Growing from Seed

Seed needs cold: stratify for three months at 2 to 5°C, then sow at 15 to 20°C. Fresh seed sown in autumn in a frame germinates the following spring. Seedlings vary, so named forms are grafted in late winter or raised from cuttings under mist.

Plant in spring, in soil that drains but does not dry out, and keep the graft union above ground. Water through the first two summers, mulch with leaf mould, and avoid pruning except to remove dead wood in winter, since the sap bleeds from cuts made in spring. In pots, repot every second year and protect the roots from freezing.

Our Take

The best small tree for autumn colour, and one whose only real demands are shade from hot sun, moisture at the roots and patience with its slow start.

Tree Seeds