Acer pictum Seeds | Painted Maple

Painted Maple (Acer pictum) seed — Painted Maple (*Acer pictum*): Sapindaceae – Acer, the genus formerly placed in its own family Aceraceae, native to Eastern Asia: China from Manchuria to Yunnan, the Korean peninsula, Japan, Mongolia and the Russian Far East, in mixed woodland and along stream sides.

LATIN NAME: Acer pictum

COMMON NAME: Painted Maple

Plant Profile

Few trees have changed their label as often as this one. The Japanese material was described as Acer pictum in the eighteenth century and the material from the Asian mainland was named Acer mono in the nineteenth, and for most of the twentieth century the two names lived side by side in different floras. Modern treatments, which look at the whole range rather than at single collections, usually treat mono as a subspecies of pictum, so the same tree appears in catalogues under both names. The subspecies themselves are numerous, and several of them, including the forms from Sakhalin, from Hokkaido and from the Korean island of Ullung, have at times been treated as species in their own right.

Cut a leaf stalk of this maple and a white latex will bead on the cut surface, a character that separates it at once from most of its relatives in the genus. The petioles are long and slender, and they hold the blade well away from the shoot, so that the crown has a light, open look in summer. In spring the small yellow-green flowers open with or just before the leaves, in upright clusters, and they are entirely without petals, which makes them easy to overlook.

The fruit is the familiar maple key, or samara, a seed in a papery case with a single long wing. The keys are borne in pairs, joined at the base and set at an angle to each other, and when they fall the pair spins like a badly balanced propeller. The spin slows the descent and carries the seed sideways, away from the parent trunk and out from under the crown, and field measurements show that the angle between the two wings is set so that the pair autorotates in a stable spiral rather than tumbling.

Because the species spans a continent, the seed provenance matters as much as the label. The northern subspecies from Sakhalin and the Kurils is the toughest and the smallest-leaved, and it is the form most often offered to growers in cold climates. The Korean and Japanese subspecies are larger and more ornamental in leaf but less dependable in a hard winter. On the Asian mainland the tree grows along streams and in mixed forest, so it prefers a moist soil, and it benefits from a sheltered site in the years before it is established.

Science & Biotechnology

The painted maple is a handsome tree of broad, rounded outline with leaves that carry five to seven pointed lobes from a heart-shaped base, each lobe with a smooth margin rather than the fine saw teeth of many Asian maples. The autumn colour is where the name comes from, and it is a warm, saturated gold rather than the scarlet of the red maples of North America. The difference is chemical: the yellow is carried by carotenoid pigments that are already present in the leaf and merely become visible as chlorophyll breaks down, while a red autumn leaf needs anthocyanins synthesised afresh in the last weeks of the season.

Maples are not easy from cuttings, and named selections of this species are usually multiplied by grafting or by budding onto seedling stock. Micropropagation offers another route. Shoot tips and nodal segments can be established in culture on a medium containing a cytokinin, and the shoots that form can be rooted after a low-auxin treatment. The technique has been used for other maples and for this species group, and its value is the same everywhere: a selected tree can be copied exactly, without the variability that comes from seed and without waiting for a graft union to take.

Uses & Benefits

The tree is host to a small community of specialists. Maple aphids colonise the underside of the leaves in spring and coat the upper surfaces with honeydew, which then blackens with sooty mould. Eriophyid gall mites cause raised, reddish blisters on the foliage of several Asian maples, and the fungus that causes tar spot lays a black, glossy patch on the leaf surface, which is disfiguring but rarely fatal. Because the species is widely planted in parks, it is also one of the maples that suffers from the horse chestnut leaf miner-like leaf blotch problems of wet summers, and the cure in almost every case is better air movement rather than more water.

Growing from Seed

Unlike the sugar maple of North America, which ripens its seed over a full year, this species flowers in spring and matures its keys in the autumn of the same season. The seed is therefore ready to fall while the weather is still mild, and it can be sown at once rather than being stored over winter.

Sow the keys as soon as they are ripe, because the seed of this group loses viability quickly once it has dried out. Rub the wing off, since it holds moisture against the seed and encourages mould, and press the seed into the surface of a moist, gritty mix, covering it lightly. Leave the pots outside through the winter so that the cold can do its work, and protect them from mice with a mesh cover. The seedlings are fast once they start, and they push a strong central root before the shoot appears.

Move seedlings into deep pots before the root reaches the base of the container, and never let them sit in water. A young maple that has been checked by a coiled root will often stand still for a season before it begins to grow.

Our Take

Painted maple is a tree for damp ground and a cold winter, and it earns its place with the autumn gold rather than with the flowers. I sow the keys in autumn and let the pots take the frost. Growers who want the large-leaved Asian maples should look at our pages on the mono maple, trident maple and the Manchurian striped maple.

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