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

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.

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

    Acer palmatum in autumnAcer japonicum 'Fairy Lights'Acer palmatum Dissectum Group in autumnAcer palmatum var. dissectumAcer palmatum var. dissectum 'Garnet'Acer palmatum 'Orange Dream'Acer palmatum 'Sango-kaku'

    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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    • rosieogrady avatar

      By rosieogrady on 26/09/2015

      Hi I was thinking about planting an Acer in a large bed, below a mature Horse Chestnut. I know that Acer's are prone to horse chestnut scale, so wondering if there are any Acer's less likely to be affected? Or if too risky any alternative suggestions? The location is London


    • RILLS avatar

      By RILLS on 17/06/2015

      Slightly different problem from those above but baffling nonetheless. My red acer stands at 6ft tall with a magnificent canopy at the tips of its branches but totally bare stems. Two years ago these stems were branched and covered in leaves however these curled and died (no scorch). Occasionally new leaves grow on these bare branches but eventually they too curl and die leaving only the very healthy canopy. Any ideas?


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    • Maurice S. avatar

      By Maurice S. on 21/03/2015

      My shoji maple was planted in 5/08, is about 6 feet tall and seems healthy except for the following problem. It is now leafing out in its usual brilliant red foliage, but as the leaves turn green later this spring they will turn brown, become dry and fall off the tree. The tree has a northern exposure and only receives direct sunlight in the morning and evening. This will happen to almost all of the leaves and they will be replaced by new leaves...and I can't remember if the same problem happened to the new leaves or not. I have examined the leaves for insects and pests; however, I have not been able to detect any. Do you have any suggestions for dealing with this problem? Thank you!


    • Helga L avatar

      By Helga L on 02/12/2014

      I planted a Japanese Maple in my garden early Sept and all the leaves have now fallen off. Will they regrow or have I lost the plant?


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    • Ian Welsh avatar

      By Ian Welsh on 29/10/2014

      My potted Acer Palmatum had a fine canopy and for years I trimmed the lower branch shoots to promote this. Then 2 years ago I decided to let them grow as I thought it would be good to have 3 layers. However the top now looks pathetic while the bottom is luxurious. The middle is neither here nor there. What should I do. Does the size of pot matter?


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    • anonymous avatar

      By anonymous on 26/07/2014

      we have a new 12 foot crimson king acer planted where a beech had to be felled as it was suffering from meripilus fungus. The acer has been doing well and is in full leaf but the leaves are now covered with a white powdery substance. What can we do?


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    • XxLinxX avatar

      By XxLinxX on 18/06/2014

      Thank you Mr N J Cade for your help. I went to my local garden centre with photo's and they said the same.Scale insect / Mealy bugs. Though on the RHS website I also saw a Woolly aphid which looked like it as well :o/ The treatment seems the same. I'm going to try rub off & wash off as much as I can. Then use the spray they recommended if I have to. They said j.maple are very delicate so trying to help it, could damage it or even kill it :o( ps..I couldn't answer in the reply box, for some reason it wouldn't submit my response there. But wanted to say thanks.


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    • XxLinxX avatar

      By XxLinxX on 18/06/2014

      Hi,I have a japanese maple in a pot.I've had it there for approx 12 years. I noticed on the leaves is a white fluffy substance.On a closer inspection I have now noticed white/brown scale on the trunk. I took a photo and when zoomed in, it to has this fluffy white substance matted over brown bits. Does anyone know the best way to get rid of this, without harming my beautiful tree.


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    • anonymous avatar

      By anonymous on 04/06/2014

      My potted acer approx 5 years old has a fungus on the trunk. What is the cause of this please? It looks in wonderful condition at the moment and for the first time has some brilliant red 'helicopters' (similar to the sycamore) at the end of each branch!


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    • Michele avatar

      By Michele on 18/05/2014

      Please help.. I cut back Acer hard in autumn . It has grown back really well but now has cream streaks/spots on the leaves and new leaves disfigured. Have looked at diseases here but doesn't sound like those.


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    • John R Humm avatar

      By John R Humm on 17/05/2014

      I have an Acer Palmatum which has recently sprouted delicate branches a third of the way down the trunk. Leaves are green and the new growth appears to be very delicate. Is this normal or do I need to prune back to the original trunk?


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    • Pam Clarke avatar

      By Pam Clarke on 11/05/2014

      I have the same problem with a young Acer. The plant is approx. 3 years old. I noticed the new leaves start to wilt about 10 days ago. Should I re pot in the Spring?


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