Japanese acers (Acer palmatum) need careful placing away from spring frosts because they are vulnerable just as the leaves emerge in April. Then a sharp frost can kill them and this can happen to large plants. However ,they are most vulnerable when small so the best advice I can give you is to buy the best specimen you can afford rather than a small whip of a plant.
Go to a specialist nursery such as Bluebell Arboretum and Nursery and try to visit personally (either in autumn or spring) and look for a named tree with a good shape.
The best conditions
You do need to have good fertile soil to succeed, as well as a sheltered site away from strong winds. Japanese acers do tolerate some lime, but they don’t grow on chalk or in very dry shade. If these are your conditions opt for a container-grown plant and ask your nurseryman for suitable suggestions because growth habit varies according to type.
Choose your site carefully
Japanese acers have been grown in Japanese gardens for centuries because they are wonderfully intricate and slow growing. In the wild these are woodland canopy trees that are protected under larger trees, often on a woodland edge, and this is the position you should aim for.
All Asian plants (including Japanese acers) are used to a rainy season in summer. Avoid frost pockets. If your garden is sloping, plant at the upper end so that cold air rolls downhill. If a severe frost is forecast just as the leaves are emerging, cover the plant with thick horticultural fleece. A good Japanese acer should be seen as an investment, so expect to part with at least £30.
Planting your acer palmatum in the ground
- Plant in clement conditions, either in spring or autumn.
- Dig a hole at least twice as wide and a little deeper than the root ball.
- If you are on heavy soil break up the bottom of the hole and add a two-inch layer (5cm) of planting compost mixed with grit.
- Water your plant well before planting. If it is very dry, soak it in a bucket of water for twelve hours.
- Plant at soil level or a fraction deeper and replace the soil and water well.
- There is no need to add fertiliser as Japanese maples do well on low nutrient levels.
- Mulch with bark and keep newly-planted acers watered in their first growing season.
Planting in a container
- Select a sturdy terracotta pot about twice the size of the one the acer is already in.
- Make sure the pot has good drainage holes and stand your pot on feet so that water can escape in winter.
- Avoid pots with narrower necks than bottoms because eventually you will have to repot your tree and this shape makes it impossible. Avoid pots which are much wider at the top than the bottom. They look sturdy, but catch lots of rainfall and this lingers round the roots.
- Use John Innes No.3 as this loam-based compost is less likely to dry out.
- Keep plants well watered while in leaf and check them every week as rainfall is often kept away from the compost by the leaves.
Training your tree
Shape varies according to type from weeping, to dome, to vase-shaped to almost contorted but growth tends to be slow. Pruning is always gentle and normally done from January to February, when you can see the shape of the bare tree. Light trimming can also be done in summer.
As many trees are seed-raised, some trees are usually grouped into different categories. The Atropurpureum Group have purplish-red foliage through the growing season. The Dissectum Group have very finely divided foliage that’s normally green. In all, there are a thousand different ones named and for sale, and some colour brilliantly in autumn.
There are lots on sale so choose one you like – here are a few recommendations.
Acer palmatum 'Sumi-nagashi'
A tree-like acer with jagged-edged seven-lobed leaves that are a rich purple in spring. These go green in summer and then redden up in autumn. This can take more exposed positions than many acers.
Acer palmatum 'Bloodgood' AGM
A really popular variety that forms a large shrub about 13ft (4m) in height. The deeply cut, purple leaves turn deep-red in autumn and this is recongnised as one of the finest for autumn colour. Tolerates a sunny position and keeps its colour throughout summer.
Acer palmatum ‘Katsura’ AGM
A medium-sized maple often grown for its new orange growth in early spring. This yellows in summer, but keeps an orange edging to the leaves. It’s upright and its five-lobed leaves provide good autumn colour in shades of yellow, orange and red. A very popular and colourful maple in spring and autumn.
Acer palmatum var. dissectum ‘Garnet’ AGM
Deeply divided, rich-purple, feathery foliage and a dome-like habit make this highly popular for containers and for smaller gardens. ‘Garnet’ holds its colour throughout the growing season and them turns yellow and orange.
Acer palmatum ‘Red Pygmy’ AGM
A mound-shaped tree with delicate, seven-lobed reddish-purple foliage that turns red/scarlet in autumn. This is a very graceful acer.
Acer palmatum 'Yezo-nishiki'
This elegant maple, suitable for garden or container, has vivid purple leaves which hold their colour well through the summer, turning scarlet before falling in autumn. Can be grown in a container for many years if required.