Japanese Maple Bonsai Care Guide
Acer palmatum is a native of China, Japan, and Korea. Literally translated, Acer is "maple" and palmatum "hand", for the five-lobed leaves bearing a resemblance to the human hand. There is a wide variety of Japanese Maples, each having different traits. This species is known for random mutations in cultivars, with variations often popping up in seedlings. It is a popular bonsai in Japan as well as in the Western world, largely because of its beautiful, often colorful foliage.
The dense foliage and stunning color variations combine with a textured, corky trunk to make this a visually striking bonsai tree. The leaves on new shoots vary from yellow to orange-ish to red, with fall colors equally as bright. Small yellowish flowers develop in late spring to early summer, and the seeds are of the familiar double-propeller type. The bark of young trees is green – red in some varieties – turning to a light gray or brown as the tree matures.
It is best kept as an outdoor tree so that it can experience a period of dormancy. It will, however, need frost protection if the temperature dips below freezing. The tree should be kept in full sun except in the hottest afternoon, when it should be placed in light shade to protect the leaves from sun damage.
Japanese Maple is a bit finicky about watering. It should be kept consistently moist without bogging down the soil and risking root rot. It should not allowed to dry out completely or it may not survive. Avoid watering during the hottest part of the day, and if it will be unattended for a long period be sure to give it access to an automatic watering source. Rainwater is best for this species as it prefers to be slightly more acidic than tap water can provide. Do not use lime-heavy water.
Feed this bonsai a nitrogen-heavy fertilizer every week to two weeks throughout the early spring as the buds need the extra boost while they're opening. After the leaves harden off give a diluted mix every other week throughout the rest of the growing season. Decrease feeding during the hottest periods of summer. In late summer use a nitrogen-free fertilizer, gradually tapering off feeding by winter.
Too little fertilization will cause short internodes on more mature trees and too much can cause legginess. Refrain from fertilizing just after repotting – wait until new growth appears and start gradually. If yellowing of leaves occurs, the plant may need a dose of acidic or alkaline fertilizer.
Popular Styles – Japanese Maples take well to many bonsai styles. Some of the best forms are informal upright, groups, twin trunk, broom, weeping, and clump.
Shoots and small branches can be trimmed throughout the year. Prune larger branches in fall to minimize bleeding, or in summer when the wounds heal faster. Cut paste should be utilized because of this tree's vulnerability to certain fungal diseases that attack through wounds.
New growth can be trimmed back to one or two leaf pairs. Leaf pruning may be done in early summer every two years in order to encourage smaller leaves to grow. To perform total leaf pruning, remove all leaves, keeping the shoot intact. Alternatively you can partial leaf prune, pinching off only the largest, most dense leaves or removing leaves in the strongest areas of foliage.
Japanese Maple bonsai are typically shaped by pruning and leaf trimming. Wiring may be done if desired, but the bark should be protected by raffia. The trunk may be directed to a slant by tying it to a stake.
Acer palmatum may be propagated fairly easily by seed, cuttings, or layering. Seeds and cuttings should be done in the summer.
Young trees (under 10 years old) should be repotted every one to two years, and more mature trees every two to three years. This should be carried out in spring, along with root pruning. The roots grow relatively quickly and can be pruned aggressively, with removal of up to half the roots' length, particularly in younger bonsai. This species has a shallow root system and so can be planted in a rather shallow container, but one that is large enough to allow for its vigorous root growth.
Insects/Pests & Diseases:
Japanese Maple is moderately pest and disease resistant, particularly if kept healthy. It can fall prey to aphids or scale, however.
Aphids can usually be removed with a spray of one teaspoon of dish liquid in a quart of warm water, applied until run-off occurs and then rinsed with a spray of plain water.
Scale may be removed with the edge of a sharp knife or by painting the shell with rubbing alcohol.
Local caterpillars can cause foliage damage so keep an eye out for these and remove them by hand.
This tree is also susceptible to fungal infections, which can be discouraged by careful attention to proper watering.