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Japanese Maple Basics
Care & Pruning
Generally, zones 5-8. Heat is a consideration, especially in the south, not necessarily for the health of the maple but for its effect on leaf color, causing many purple or red-leaved varieties to “go green” in the summer. They typically leaf out early in the season and a late cold snap can cause serious damage even to mature specimens.
Varieties from 8 to 30 feet tall and wide.
Providing the right amount of light can be a balancing act. Too much light can damage delicate leaves. Too little light, and some of the more colorful varieties will take on a greenish tone — still attractive, but not the brilliant fall color of reds and purples as would be expected. For best color, most maples need a location with part day's sun or at least high light.
Famous for their phenomenal fall colors, Japanese maples also present purples, reds, yellows, oranges, and greens as well as variegation throughout the growing season.
Most Japanese maples grow at a slow to moderate rate of 1 to 2 feet per year. They typically grow fastest when they are young and slow down as they reach maturity. Planting them in a spot where they are happy and caring for them well helps maximize their growth rate. If you want an established look right from the start, you can opt to plant an older, larger maple rather than a young one that may take years to mature. If this isn’t an option, select a cultivar that has a reputation for being a faster-than-average grower, such as Acer palmatum ‘Beni otake’.
When to plant:
Fall is an excellent time to plant because it allows the roots of your Japanese maple to get established while the rest of the tree is dormant. However, many gardeners also find success planting in the spring. Either way, make sure there is no threat of frost which can damage a newly planted tree.
Japanese maples prefer to be in locations protected from strong winds and spring frosts.
Japanese maples are fairly adaptive, but prefer moist, well-drained, slightly acidic soils that contain organic matter. If you live in an area with heavy clay soil, planting them slightly elevated is beneficial; this will help guard against root rot and disease. Chlorosis (yellowing of leaves due to lack of chlorophyll) may occur in high pH soils.
Many of the smaller varieties are excellent in containers. Japanese maples “self stunt,” meaning their top growth will decrease when their roots are confined. When planting in a container, it is still wise to focus on small to medium varieties or dwarf forms.
Water them well at planting time and regularly thereafter. Although they can endure periodic dry spells once established, you will want to avoid moisture extremes and water regularly during extreme drought. Maples like mulch to protect their roots from heat and cold, as well as reduce the frequency of watering, especially for those in containers. Keep mulch several inches away from the trunk.
Low nitrogen fertilizer is fine in spring (15 degrees or lower), but don’t apply after November, as this could impede fall color & winter toughness. It is best to wait to fertilize newly planted Japanese maples until their second growing season.
As a rule, Japanese maples don’t require regular pruning and will create their own naturally beautiful shape. However, if you want to create an airy look, thin out branches over time; to create a canopy, remove lower limbs. Japanese maples are an exception to the common pruning times of fall and winter because of the sap that will ooze from the cuts in those seasons; this can lead to disease and a weakened tree. The best time for pruning is July-August when sap won’t ooze from the branches. Because many Japanese maples are grafted, any shoots that grow from the base of the plant should be removed as these can become stronger than the grafted section and overtake it.
Problems, Diseases, Pests:
For the most part, Japanese maples don’t suffer from any serious insect or disease problems. They can be susceptible to stem canker, leaf spots, fusarium, verticillium wilt, botrytis, anthracnose, and root rot. Mites can be troublesome, and other pests may include aphids, scale, borers, and root weevils.