How To Grow Japanese Maples
Japanese maples give outstanding autumn colour
They belong to the Acer family and are small to medium deciduous trees, which grow either upright or in a dome shape. They originate from Japan, North and South Korea, south east Russia and eastern Mongolia. They were first brought to England in 1820, and are ideal for our cool, damp climate. They are an essential part of Japanese style gardens and have long been popular as a bonsai tree. There are over 1,000 cultivars, and are relatively disease free. As the root system is fairly compact they are ideal for small gardens and containers. The upright palmatums can reach a height of 6 – 10m (20 – 33’), the dome shaped dissectums can grow to between 1.2 – 7.5m (4 – 25’) wide. As they are very slow growing it will take them many years to reach these dimensions and the eventual height and width also depends upon the variety.
They are one of the best plants for giving outstanding autumn colour. A Japanese style garden is very easily achieved by under-planting with hostas and ferns and just adding some statuary in the form of a large stone bowl, a figure, a minimalist water feature or a lantern. Mulching with stone chippings completes the effect and you have an easy to maintain stylish garden.
They need a well-drained loamy soil, slightly acidic with a good organic content. They will not thrive in wet or dry soils or a very alkaline soil. They tend to grow in the understory of a woodland so need dappled shade. The trees with red and purple coloured leaves need more sunshine to develop the rich hues, but not the midday sun. The variegated and pale leaved varieties can only tolerate early morning or late afternoon sunshine as their leaves scorch easily. The darker green leaved varieties are more tolerant but still cannot stand the midday sun. Strong winds can also result in scorched leaves, especially when the leaves are just unfurling in spring. So a site out of the wind is essential. Late frost can also damage new growth if it comes after a warm spell, so keep an eye on the forecast when it has put on new growth. If frost is forecast just throw some horticultural fleece over the tree. If all these conditions are met the trees are perfectly hardy.
Bare root trees can be planted in the autumn when the soil is still warm and they can grow some roots to give them a good start when they start growing again in spring. Container grown trees can be planted from spring through to autumn. Dig a hole slightly larger than the container or extent of the roots and loosen the soil in the bottom of the hole. Plant to the same depth as it is planted in the pot. Don’t add any fertiliser as this only encourages soft weak growth.
Keep the soil damp in dry spells as they need sufficient moisture to combat the drying effects of the sun. Feed with a slow release fertiliser sparingly in spring or early summer as this will again encourage spindly weak growth. Mulch every 2 – 3 years with garden compost or well-rotted farmyard manure, this keeps the soil cool and damp, keep the mulch away from the stem as this can lead to rotting.
As a rule they do not need any pruning. Just remove any damaged stems from the palmatum types; from November to early February as they bleed if cut at any other time and this can weaken the tree and open it up to infection. The dissectum types do not need any pruning. If long weak shoots spring out of the normal tree shape don’t remove them as this only encourages more to grow. They often produce these shoots as a response to initial pruning, so only prune if absolutely essential. Eventually these shoots will strengthen and produce side shoots.
Choose a container only slightly larger than the pot it is already in and put a thick layer of crocks in the bottom to ensure good drainage. Use a good loam-based compost, such as John Innes No 2. Keep the compost evenly moist. Feed with a slow release fertiliser in spring or early summer. Repot every 2 – 3 years in April or September. Just increase the size of the pot gradually as too big a pot holds too much water in winter and can lead to the roots rotting. A tree in a container is more vulnerable to freezing in winter so wrap the pot in bubble wrap and put fleece over the actual tree (don’t use plastic as this encourages condensation which rots the tree). Stand the pot on pot feet so that the water drains away from the hole; if left standing on the ground the water can sit under the pot and any silt washing through the compost will block the drainage hole.
Acer shirasawanum 'Aureum'
shirasawanum 'Aureum' - upright, layered; height 4 - 8m (13 - 26'); lime/yellow foliage in spring and summer , gold with red edge in autumn; crimson flowers
‘Okushimo’ – palmatum type; height 8m (26’); yellow and gold autumn colour
‘Senkaki’ – palmatum type; height 5m (16’); gold, yellow and coral red in autumn; coral red stems
‘Osakazuki’ – palmatum type; height 6m (20’); scarlet and orange autumn colour
‘Bloodgood’ – palmatum type; height 5m (16’); deep burgundy foliage, scarlet in autumn
‘Hana Matoi’ – dissectum type; height and spread 2- 3m(6 – 10’); variegated foliage in shades of cream, pink and red turning red in autumn
Acer palmatum 'Atropurpureum'
‘Shindeshojo’ – palmatum type, height 2m (6’); red in spring and autumn; layered shape
‘Katsura’ – palmatum type; height 3 – 4m (10 – 14’); leaves edged in orange turning orange, yellow and red in autumn
‘Seiryu’ – palmatum type; height 2 – 3m (6 – 10’); bright red autumn colour
‘Deshojo’ – palmatum type; height 2m (6’); amber foliage in spring, green in summer and red in autumn
'Viridis' - dissectum type; height and spread 2m (6'); light green lacy foliage turning crimson in autumn
‘Crimson Queen’ – dissectum type; height and spread 3m (10’); lacy burgundy foliage turning crimson in autumn