Japanese maple (Acer palmatum) is a medium-sized, showy ornamental tree whose vibrant red spring and fall foliage distinguishes itself in the garden. This deciduous tree is well regarded for its architectural shape and attractive leaves. Most Japanese maples do well in U.S. Department of Agriculture plant hardiness zones 5 through 8, although a few varieties, such as "Ever Red" will tolerate USDA zone 9. Japanese maple is a tree species that easily mutates, and hundreds of varieties are available, all with different growth habits and sizes. Mature height ranges from 6 to 50 feet, with most varieties in the 15- to 25-foot range.
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Japanese maple's most distinguishing feature is its multi-lobed, palm-like leaves, which emerge brilliant red in spring, become green during summer and change to purple, red, yellow or orange in fall. Variegated types are especially attractive -- they can be stippled, marbled, edged, splashed, or striped with white or cream -- although many gardeners complain that leaves of variegated Japanese maples permanently revert to solid green over time.
Most Japanese maple varieties prefer partial sun, preferably with an eastern sunny exposure to promote leaf coloration, with protection from the western sun. Japanese maples do well in most types of soil. A loose media works nicely -- 40 percent fine silt or sand, 20 percent peat moss and 40 percent organic compost. Japanese maples prefer a soil in pH range 6 to 8. Water deeply twice a week; water more often if it is a newly planted tree or a container-grown tree. You'll see quick growth when growing conditions are correct.
Mulch your Japanese maples with 2 1/2 to 3 inches of shredded bark, preferably hardwood, to insulate the roots and prevent water from evaporating around the tree. Pull the mulch away from the trunk slightly to prevent crown rot and insect damage. Protect your tree by covering them with sheets or light blankets from late spring frost, since the tree tends to leaf out early. Winter is the best time to corrective prune these trees to remove dead, diseased or interfering limbs. The crown can be shaped as you like to achieve landscape goals.
Keep your Japanese maple looking its best by being aware of a few problems that may plague the tree – lack of water being among the most serious issues. Japanese maple is also susceptible to leaf spot diseases that may disfigure leaves and cause early defoliation. These can be treated with a fungicide designed for treating tar spot and phyllosticta. Finally, several insects may attack Japanese maples, including scales, aphids and Japanese beetle. Biological controls such as nematodes or ladybugs are effective against these pests. Neem oil is another capable treatment.