Japanese maples are surprisingly easy to grow and flexible enough to tolerate a wide range of soils and even some shade. For the best color, grow them in full sun with afternoon shade, especially in the hottest regions.
Selecting a Site
The best location is a sunny spot with afternoon shade. Red and variegated leaves need relief from the hot afternoon sun, but won't attain full color in deep shade, and golden leaves will remain green in shade. Shade has another drawback: It can make these maples prone to fungal disease. Choose a site that can accommodate the tree's mature size. If you want to grow a tree two feet from the front of the house, choose a dwarf variety; in an enclosed backyard, an upright type is best. As for soil, a sandy loam with low to moderate organic matter is ideal, but Japanese maples accept varying soils.
Watering and Fertilizing
Newly planted Japanese maples require uniform soil moisture: Water deeply at least once a week during the growing season. Do not allow the soil to remain soggy and never site trees in standing water. Spread coarse bark mulch around the trunk to retain soil moisture and to deter weeds. Be sure the soil is moist before the ground freezes in fall.
If planted in moderately rich soil, Japanese maples do not require additional fertilizer, but you can apply an all-purpose fertilizer in spring before the leaves emerge if you desire. Like too little light, too much fertilizer can mask the desired coloration (or even the shape) of leaves.
Most Japanese maples require pruning and shaping. Begin shaping the trees two to three years after planting. Prune lightly to shape throughout the season, but leave heavy pruning until the tree is dormant. Always prune out any suckers from below the graft union as they appear. To highlight the cascading and undulating branches of some cultivars, consider pruning out the inside growth to reveal the beautiful woody form.
Pests and Diseases
Although pests such as aphids, spider mites, thrips, leaf hoppers, and others can infest Japanese maples occasionally, they rarely affect the health of the trees. Unfortunately, Japanese maples are susceptible to various fungal infections, including verticillium, fusarium, and botrytis, resulting in wilt and dieback. Because it's difficult to cure these infections, the best approach is to try to deter them by keeping plants as healthy as possible, watering in the morning, and choosing a well-ventilated planting spot. To prevent diseases from spreading, prune out any affected areas and clean your pruning tools with alcohol in between cuts.