The Japanese maple, Acer palmatum, is a slow-growing ornamental tree or shrub that reaches a maximum of 20 feet high and wide only after many years. Originating in the Orient, it performs well in USDA growing zones 5 through 8. This tree succumbs to some pests and diseases when healthy, but shows greater susceptibility when stressed by poor growing conditions. The exact process to revive a Japanese maple depends on what specifically ails it, but good maintenance practices improve the overall health of this tree.
Determine if the apparent problem with your Japanese maple truly is a problem or just a natural occurrence. For example, Japanese maples with variegated leaves sometimes lose their color, turning a more common green. Though this might be a result of an excessively shady growing site, it also happens naturally at times in juvenile trees as they grow. If a variegated cultivar continues to produce green leaves, prune that branch off the tree, but wait at least one full growing season to see if it self-corrects.
Move newly planted trees to a location with ideal light conditions if they show signs of poor growth, such as wilting, lack of color or leaf loss. Choose a location with morning sun and afternoon shade for best results. Avoid western exposures to limit heat stress, especially in the southern portion of this tree's growing range. In northern climates, the Japanese maple survives well in full sun to light shade. Certain cultivars work better full sun, including Beni shi en, Fireglow and Tamukeyama.
Check for insect pests and diseases, especially in cases where the tree already struggles in poor growing conditions. Ensure good drainage and air circulation to reduce the risk of such problems. Apply Phyton-27 annually as both a preventive measure and a control method for fungal and bacterial diseases. Aphids, scales and borers sometimes infest Japanese maples, with symptoms including leaf wilt and drop, honeydew and webbing over the branches and foliage. Use horticultural insect sprays to control insect pest populations.
Water, fertilize and mulch annually to maintain healthy growth. Japanese maples prefer, moist, well-draining soils and exhibit poor drought tolerance. Water at least an inch per week in dry weather. Watering also minimizes scorching, while fertilizing improves nutrient availability, lessening the risk of poor root growth and development. Fertilize in the spring with a slow-release, balanced fertilizer. Keep 2 to 4 inches of mulch under the canopy of this tree to maintain more constant soil temperatures while protecting shallow roots from heat, drought, pests and disease.