Japanese maple

Japanese maples (Acer palmatum) are small, deciduous trees grown for their graceful habit, autumn colour and beautiful foliage which may be coloured or deeply dissected. Many acers grow extremely slowly and are perfect in a smaller garden, grown in large containers.

Acer

Acer

Quick facts

Common name: Japanese maple
Botanical name: Acer
Group: Trees
Flowering time: Early to mid-spring
Planting time: Autumn
Height and spread: 1.2m-8m (4ft-25ft) wide and high, depending on cultivar
Aspect: Sheltered/sun/partial shade
Hardiness: Hardy with shelter from late frosts and cold winds
Difficulty: Easy

Cultivation notes

Acer palmatum is a small deciduous tree, which has been in cultivation for over three hundred years in Japan. Sometimes called the mountain maple it is found at altitudes up to 1,100m (3,600ft). It is also indigenous to forested areas in Korea and China and as far south as Taiwan. The species can attain heights of 8-9m (26-30ft) in fifty years, depending on growing conditions, but most cultivars are small, slow-growing trees.

If your soil is slightly acidic, sandy, well-drained loam with a good amount of organic matter, then you have the perfect conditions to grow Japanese maples. Do not worry if you have not; most can be grown in other soils. However, they will not tolerate wet, dry or very alkaline conditions.

Japanese maples will grow best in a sheltered position. Red and purple leaved cultivars need some sun to develop fully their dark hues. Variegated Japanese maples need partial shade to prevent the afternoon sun from scorching the foliage. Green-leaved forms tolerate full sun, but are best in dappled shade as very bright conditions can sometimes cause scorch.

Most acers have shallow fibrous root systems that resent competition from other plants, so ensure that they are not too crowded.

For successful establishment, plant at the correct level and ensure that mulch does not come into contact with the collar.

Mulch every couple of years with well rotted garden compost or well-rotted manure.

Growing in containers

Japanese maples are ideal plants for growing in containers. Plant in a loam-based compost, which allows good drainage and has a high percentage of organic matter, such as John Innes No 2 or John Innes Ericaceous.

Keep the compost evenly moist, but not soaking wet and feed in spring and early summer with a slow-release fertiliser or liquid feed.

Your maples will need repotting into a slightly bigger container every couple of years. April or September are ideal months to do this.

The roots of maples in pots are vulnerable to frost over winter, so wrap containers with a sheet of bubble wrap, held in place with garden twine.

Pruning and training

Acer palmatum is best pruned when fully dormant (November to January), as maples bleed sap from pruning cuts at other times, weakening the tree. However, pruning is still best kept to a minimum as the most graceful shape comes from a tree that has been allowed to develop fairly naturally. As a result, just remove badly-placed or crossing shoots to encourage a good framework of branches to form.

Where you do need to reduce height and width, follow long branches back to a side branch and pruning it out at this point. This is not necessary on prostrate-growing trees because they should be allowed to spread naturally to gain the best effect.

Propagation

Japanese maples can be propagated from softwood cuttings (especially vigorous cultivars such as A. ‘Osakazuki’) or from seed. Named cultivars are unlikely to come true from seed but can result in some interesting seedlings.

Cultivar Selection

Japanese maples come in many shapes, sizes, leaf colours and leaf shapes. Choose from the handful below or from the RHS Plant Selector.

Links

RHS Find a Plant
AGM Plants

Problems

Japanese maples can be very prone to leaf scorch in windy or excessively sunny positions, particularly those with fine-cut leaves. Young leaves can also be caught by frost.

Poor autumn colour or purple-leaved varieties turning green may suggest a lack of light.

Containerised specimens may be troubled by vine weevil larvae. Japanese maples are susceptible to scale insect damage, including horse chestnut scale. Coral spot, Phytopthora root rot and verticillium wilt can also be a problem.


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