Advice
RHS Help & Advice
Acer palmatum cultivation
Acer
palmatum is a small hardy deciduous tree - commonly called
Japanese maple, which has been in cultivation for over 300
years. Most cultivars are small, slow growing trees ideal
for containers or smaller gardens.
Garden cultivation
Acer palmatum prefers a slightly acidic, sandy, well-drained loam with a medium amount of organic matter. However, most cultivars will adapt well to other soil types, but they will not tolerate wet or dry conditions or very alkaline soils.
Most have shallow fibrous root systems and do not compete with other plants. When planting make sure the hole is large enough to accommodate all the roots. If the plant is container-grown tease out the roots first. On heavier soils, break down the sides of the hole with a fork.
Green-leaved cultivars will tolerate full sun but in extremely hot conditions they may scorch. Some afternoon shade can prevent this from happening. Variegated forms need partial shade to prevent the afternoon sun from scorching the foliage. Red-leaved cultivars need some sun. They cannot develop their deep red colour without the benefit of full sun for some of the day.
Container cultivation
Japanese maples adapt well to life in a pot if the compost is kept evenly moist (not wet). Plant into compost, which allows good drainage, aeration and has a good loam content, with a high percentage of organic matter such as John Innes No 3. Feed containerised maples in the spring and early summer. Re-pot every couple of years if necessary. In winter protect the roots by covering the pot with bubble wrap and raise the pot from the ground to aid drainage. Avoid placing pots in full sun.
Problems
Leaf scorch is caused whenever water is lost from the leaves faster than the roots can take it up. A wide range of environmental factors causes this such as frost, drought, drying winds, hot sun and even salt-laden winds in coastal areas. Foliage will turn brown particularly around the margins and veins, then curl and shrivel. Sometimes symptoms are not visible until later in the season. Scorch does not usually kill; plants showing symptoms should be thoroughly watered and sheltered if possible.
Maples can be prone to attack by vine weevil, aphid and scale insects.