Acer palmatum spp.
The Japanese Maple (Acer palmatum) is originally from Japan, China and Korea. It owes its botanical name to the hand-shaped leaves with in most cases five pointed lobes (palma is the Latin word for the palm of hand). The bark of younger trees is normally green or reddish and turns light grey or grayish brown with age.
The greenish yellow flowers stand in clusters and appear in May - June. They develop into maple seeds shaped like little paired winged nuts which float to the ground like propellers when mature. There are countless cultivars of the Japanese Maple with manifold leave colors and shapes and diverse habits and sizes, which are very popular as ornamental shrubs. These include Kiyohime, Kashima, Shishigashira and Arakawa. Red leaved cultivars include the Deshojo and Seigen. The young shoots in spring have yellowish, orange or even bright red leaves. The Japanese Maple is also well-known and popular for its very attractive yellow, orange and red autumn colors.
Specific Bonsai Care Guidelines for the Japanese Maple Bonsai
The Japanese Maple prefers a sunny, airy position but during great midday heat it should be placed in the light shade to prevent damaged leaves. The Japanese Maple is frost hardy even when trained as a Bonsai, but it should be protected from strong frost.
A Japanese Maple in a Bonsai pot must be watered daily in most cases during the growth season, maybe even several times a day during the hottest days, if the soil is well-drained and the tree healthy and vigorous. Use water deficient in lime as the Japanese Maple prefers a neutral or slightly acid pH-value.
Especially for mature Japanese Maple Bonsai the use of solid organic fertilizers is well-proven, as it takes effect slowly and gently and generally contains all the required micronutrients. Follow the dosage instructions carefully. If stronger growth is desired, for example on young plants or raw material, you can additionally use a liquid fertilizer weekly. But avoid fertilizers with a very high nitrogen concentration because this would provoke unnecessarily large internodes and leaves.
Trimming of shoots and twigs can be done year-round. The pruning of strong branches should be done in autumn to prevent excessive bleeding, or in the summer when callus growth is quick. It is advisable to apply cut-paste as the Japanese Maple is vulnerable to some fungal diseases which can enter through wounds. Cut new growth back to one or two pairs of leaves. Mature Bonsai with a delicate ramification can be pinched in order to keep the twigs thin. After the first leaf pair has unfolded, remove the soft little tip of the shoot between them. This method weakens the tree in the long run and should be applied specifically and thoughtfully.
Leaf pruning (the removal of leaves during the growing season) can be done every other year in early summer to encourage smaller leaves. Remove all the leaves, leaving the leaf-stems intact. Partial leaf pruning is more gentle. You do not remove all the leaves, but only the largest and closely spaced ones or you remove the leaves in the strongest areas of the tree. Partial leaf pruning can be done each year as it does not stress the tree as much as total leaf pruning.
Wire the trees early when the wood is still pliable. Becomes much harder to wire once branches have began to set. Also be sure to watch the wire closely as once it digs in the scars will be very persistent.
Repot Japanese Maple Bonsai once every two years and prune the roots efficiently. Root growth is strong and the pot is totally filled with roots after a short time. Use a well-drained soil mixture, for example Akadama mixed with Pumice and lava rock.
The Japanese maple can easily be propagated by seeds or cuttings in summer. Air-layering is also a quick and easy propagation method for Japanese Maples.
Pests / diseases:
The Japanese Maple is quite a sturdy tree species. But in spring it is often affected by aphids, which can be eliminated with customary insecticide sprays and sticks to push into the soil. Overly wet leaves can also lead to grey mildew forming and covering the leaves.