Japanese maple 'Osakazuki'

Sun

Full sun to partial shade; morning sun and afternoon shade are safest in hot climates. Protect from strong, drying winds.

Water

Keep the root zone evenly moist but not waterlogged. Water deeply during dry spells, especially in the first two to three years after planting.

Soil

Well-drained, humus-rich soil, preferably slightly acidic to neutral. Avoid waterlogged ground and very shallow, dry or strongly alkaline soil.

Height

15-25 ft (4.6-7.6 m)

Spread

15-25 ft (4.6-7.6 m)

Foliage

Deciduous, broadly hand-shaped leaves, usually with seven pointed lobes. Green through summer, turning vivid crimson in autumn; colour intensity varies with weather and growing conditions.

Growth

Slow to moderate; allow roughly 15-20 years to develop a substantial crown.

Care needed

Medium

• Wildlife

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   7 ft (2 m)

2. After 1 year

   7 ft (2.2 m)

3. After 2 years

   8 ft (2.3 m)

4. After 3 years

   8 ft (2.5 m)

5. After 5 years

   9 ft (2.8 m)

About 26 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Safe

Invasive in

the US

Growth rate

Slow

• Plant with the root flare at soil level and leave space for the mature crown.
• Water deeply when the soil begins to dry; do not keep the roots constantly saturated.
• Apply 2-3 in (5-8 cm) of leaf mould or bark mulch, keeping it clear of the trunk.
• Feed lightly in spring only if growth is weak or the soil is poor; avoid heavy nitrogen feeding.
• Protect young growth from late frost and shelter the tree from hot afternoon sun and drying winds.
• Remove any shoots growing from below the graft union.

Pruning. Prune sparingly in early to midwinter, removing dead, damaged or crossing branches and preserving the natural outline. Avoid heavy pruning and late-winter or spring cuts, which can bleed sap.

Autumn

Plant while the soil is workable in mild regions; in cold regions, postpone planting until spring.

Early winter

Once the leaves have fallen, inspect the branch structure and make only necessary pruning cuts.

Spring

Plant in cold regions once the soil is workable, refresh mulch and check for shoots below the graft.

Late spring

Protect newly opened leaves with horticultural fleece if a late frost is forecast.

Summer

Check soil moisture during dry weather and water deeply before drought stress causes leaf scorch.

Autumn

Collect fallen leaves for leaf mould and remove unwanted seedlings nearby.

• Use as a lawn or courtyard specimen with enough space to show its broad branching outline.
• Place against dark evergreen shrubs to make the crimson autumn foliage stand out.
• Combine with ferns, hostas and shade-tolerant groundcovers in a sheltered woodland border.
• Set beside a path or seating area where its leaf shapes and seasonal changes can be seen closely.

Garden styles it suits: Japanese, Woodland, Autumn colour, Zen dry garden, Pacific Northwest woodland and English country.

Plant it with: Hostas, Epimediums, Japanese forest grass, Christmas fern, Camellias and Rhododendrons.

Wildlife: The crown provides shelter and perching sites for small birds, and the inconspicuous spring flowers are visited by insects. It generally supports fewer specialist native insects than locally native maples.

• Brown, crisp leaf margins: usually caused by drought, drying wind or intense sun. Water deeply, mulch and improve shelter; damaged leaves will not turn green again.
• Late-frost damage: young leaves may blacken or collapse. Protect small trees when frost is forecast and wait for replacement growth before removing damaged shoots.
• Verticillium wilt: sudden wilting or branch dieback can indicate this soilborne disease. Seek a diagnosis, prune dead wood and avoid replanting another susceptible tree in affected soil.
• Scale insects: inspect twigs for fixed bumps and sticky honeydew. Remove small infestations by hand or use a labelled horticultural oil at the appropriate season.

Japanese maple is not known to be toxic to people, cats, dogs or horses. It should not be confused with red maple (Acer rubrum), whose wilted or dried leaves can cause fatal poisoning in horses; do not assume all maple leaves are safe forage.

Where it spreads. Japanese maple can escape into woodland and is locally invasive in parts of the eastern United States, particularly the Mid-Atlantic. 'Osakazuki' can produce seedlings, which will not reliably resemble the parent; remove volunteers near natural areas and check local guidance before planting.

• Japanese maple 'Ichigyoji' (Acer palmatum 'Ichigyoji')

  Similar green leaves and upright habit, but autumn colour is usually yellow to orange rather than the strong crimson typical of 'Osakazuki'.

• Full moon maple (Acer japonicum)

  Its leaves are generally rounder, with more lobes, commonly seven to eleven, and are often noticeably hairy when young. 'Osakazuki' usually has seven more distinctly pointed lobes.

• Green-leaved Japanese maple (Acer palmatum)

  Seed-grown trees can look very similar in summer, but their leaf shape, habit and autumn colour vary. A reliable nursery label is the best way to confirm 'Osakazuki'.

The species name palmatum refers to the hand-like shape of the lobed leaves.

Propagation. Usually propagated by grafting onto Japanese maple rootstock to preserve the cultivar. Seedlings are variable and cannot reliably be grown as 'Osakazuki'; grafting is generally a specialist nursery task.

Accepted botanical name

Acer palmatum

In the US and Canada

Introduced in Canada and the lower 48 states.

Native range

Japan and Korea.

Measured

Soil pH 6.5 to 7. Average height 700 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.