Japanese maple

Japanese maple: how do you recognise it?

Habit

Shrub or small tree of 2–8 m, often broad and layered; some cultivars stay under 2 m.

Leaf

Opposite, 5–10 cm, with 5–9 pointed, toothed lobes; green or red, superb autumn colour.

Bark

Smooth, grey or green; young shoots sometimes red.

Flower

Small reddish-purple flowers in May.

Fruit

Small winged nutlets.

Difference from silver maple

Silver maple is a large tree with silvery leaf undersides.

Flowering: April–May · Pruning: July–August and November–December

Identify by feature: Palmate leaves · Opposite leaves · Winged seeds

Looks like it, but isn’t

• Silver maple Acer saccharinum: a large tree with silvery leaf undersides. Difference from silver maple

Why grow it?

• Beautiful leaf shape and colour from spring to autumn, with stunning autumn colour.
• Grows slowly and stays small: suitable for small gardens, borders and large pots.
• A graceful outline, even in winter without leaves.
• Hardly needs pruning.

Japanese maple: where does it grow best?

• Partial or light shade, sheltered from wind; in full midday sun the red and finely cut cultivars in particular will scorch.
• Humus-rich, slightly acid, free-draining soil that doesn’t dry out; no wet feet and no heavy, waterlogged clay.
• Not in a frost pocket where late frosts linger: they damage the young leaves.
• Allow 3–4 m width for a mature small tree; dwarf cultivars fit in a large pot.

Light

Partial shade

Legal basis

Acid soil

Moisture

Normal

Size

8 m tall, 4 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Rhododendron: Likes the same acid, humus-rich soil and light shade.
• Japanese pieris: Evergreen, with sprays of small flowers in spring, for the same acid soil.
• Ferns: Their fine fronds beneath the maple create a calm, Japanese feel.
• Hostas: Large leaves in the shade under the small tree, contrasting with the fine maple foliage.

Japanese maple: when and how to plant it?

1. Plant in October–November or in March–April, root-balled or container-grown.
2. Dig a wide but not too deep planting hole and mix in leaf mould; on chalky soil, some peat-free ericaceous compost helps.
3. Don’t plant it deeper than before and firm the soil gently.
4. Spread a layer of leaf mould or wood chips over the roots: this keeps them cool and moist.
5. In a pot: a large pot with a drainage hole, a layer of gravel for drainage and good potting compost.

Care

Watering

Regularly in the first year and in dry summers; often in a pot, but without letting the roots stand in water.

Feeding

Sparingly: a little leaf mould in spring. Too much fertiliser gives soft growth.

Mulch

Renew the layer of leaf mould or wood chips over the roots every spring.

Pot

Repot every 2–3 years in spring, or replace the top layer of compost.

Tip: Choose the cultivar to suit the spot: finely dissected cultivars (the Dissectum group) are the most sensitive to sun and wind; those with larger, green leaves are the toughest.

Japanese maple: when to prune it?

Pruning months: July–August and November–December.

When: In summer or late autumn; not in spring (it bleeds).

How:

• Hardly needs pruning. Only remove crossing or dead twigs, close to a side branch.
• Keep the natural, layered shape: never simply shorten all the branches, as that gives ugly clusters of shoots.
• On a grafted cultivar, remove shoots that grow from below the graft, with different leaves.

Caution: Don’t prune from late winter through spring: the maple then bleeds a lot of sap from every wound.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Sowing

Sow fresh seed outdoors in autumn; it needs a cold period and germinates in spring. Seedlings rarely resemble the parent cultivar.

Grafting

Nurseries graft cultivars onto a seedling; for an amateur gardener it is tricky.

Japanese maple: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Hardy; it is mainly the young leaves in April–May that are sensitive to night frost.
• In a pot the roots freeze more quickly: put the pot in a sheltered place against a wall and wrap it up in severe frost.
• Without leaves it shows off its graceful shape; in some cultivars the twigs turn coral red in winter.

Diseases and pests

• Verticillium wilt: Branches suddenly wilt in summer, sometimes on one side of the shrub; the wood shows dark streaks. There is no cure: cut diseased branches back into healthy wood and don’t plant another maple in that spot.
• Leaf scorch: Brown, dry leaf edges in summer from strong sun, drying wind or drought. Water in good time or move it to a more sheltered spot.
• Late frost: The young leaves shrivel after a cold night in April. It usually reshoots; cover small plants if frost is forecast.
• Aphids: Sticky leaves in spring; natural predators usually deal with them.

Through the year

• March: Planting is possible; don’t prune yet (it bleeds).
• April: Young leaves: protect from late frost.
• June: Water in dry spells, especially in a pot.
• July: Summer pruning: remove dead and crossing twigs.
• August: Last summer pruning; watch out for leaf scorch.
• October: Autumn colour; planting.
• November: After leaf fall you can prune again.
• December: Last pruning month; protect pots from frost.

What can you use it for?

Garden and landscape

Small ornamental tree for small gardens, borders and large pots; stunning autumn colour.

Did you know?

• There are hundreds of cultivars, from dwarf forms to small trees with finely dissected leaves.
• In Japan, many people visit temple gardens and mountains in autumn to admire the red maples; this is called momijigari.
• ‘Palmatum’ means hand-shaped: the leaf looks like an open hand.
• The species name palmatum means ‘hand-shaped’: the deeply cut lobes resemble the spread fingers of a hand.
• In Japan, crowds head to the mountains and temple gardens in autumn to admire the red maples. This is called momijigari, ‘hunting for red leaves’.