Japanese Maples are a widely cultivated family of beloved, slow growing plants useful as small trees, large shrubs, container plants and bonsai. They make perfect landscape accents for any size yard and are hardy in Zones 5-8. Hundreds of cultivars exist, and each has its own unique foliage form and color, growth habit, fall leaf display and size. Technically, any maple native to Japan is considered a Japanese Maple. In common use, Acer palmatum is the intended species with Acer japonicum and Acer shirasawanum thrown into the mix.
Japanese Maple cultivars fall into broad groupings within the species based on their leaf form andcolor. Those belonging to the dissectum group, for example, have deeply serrated leaves that appear finely textured and almost fernlike. These maples are nicknamed Lace leaf or Cut leaf Maples. Theatropurpureum group has red-purple foliage and is known as Japanese Red Maple.
CULTUREJapanese Maples grow in sun or shade, but in hot summer climates they prefer light shade during thehot part of the day. In their natural habitat, Japanese Maples are understory trees, growing in dappled forest sunlight and at the edges of woodlands. Ideally, they prefer to be grown in similar conditions. Thecool areas of your garden where you would choose to sit in the summer are the same areas where thesemaples would like to be planted. Very bright sunlight and hot summers do not kill trees, but new leavesmay scald and burn in these conditions, especially the first year or two after planting. Varieties with variegated leaves are especially sensitive to burn. Site Japanese Maples in protected NE or N facing areas away from wind. These lovely trees leaf out early in the spring, so avoid frost pockets, spots which receive the full warmth of early morning winter sun, and exposed locations where they may be hit hard by spring frost.
Plant Japanese Maples in slightly acidic soil with plenty of organic matter. Soil MUST be loose, well drained and well aerated. Soggy, heavy clay soil around the roots is a killer – especially in the winter.To improve the tilth and drainage of clay, add gypsum and well-aged bark mulch to create a wide, low mound 3-4 inches above grade.
Plants should have a CONSISTENT supply of water during the first 2-3 years after planting. Maple rootsare shallow, so water often BUT not deeply to keep soil moisture even without drowning your trees.Established trees can withstand considerable dry spells and even periods of drought, but young trees may dry up and die under the same circumstances. A lack of water during the early years of establishment is the number one killer of young trees and drought damaged trees often don’t show symptoms until thenext season when it is too late to help them.
When planting Japanese Maples, it is EXTREMELY important that they ARE NOT set in too deeply. The spot where the trunk flares out to meet roots should be soil level. Mulching is highly recommended, for it helps keep roots cool and moist, but limit the amount of mulch you use to 2-3 inches. Use only well aged bark or compost and keep it pulled away from the base of your tree. Planting or mulching too deeply can kill your tree. Japanese Maples planted in the ground need no fertilizer. Protect your trees from lawn food, for it will burn maple roots.
PRUNINGJapanese Maples have a naturally beautiful form, so prune only to remove suckers, damaged stems andcrossing branches or to lightly groom your tree. Thin out canopies a bit with pruning to improve air circulation and decrease the chance of fungal disease or rot. Maples have two growth periods. One is inearly summer and the other at summers end. Spring growth is less vigorous than late summer growth.If you wish to contain the size of your maple, simply prune back all the long, late summer growth. Thiswill keep your cuts less than a fingers width in size and retain the natural shape of your tree. Larger cutsshould be made in early spring just as buds swell. Be sure to keep your pruners sanitized.
TROUBLESHOOTINGFew pests or diseases afflict Japanese Maples, and no regular spraying or controls are needed. Mostproblems that occur with these lovely trees result from improper siting, planting or follow-up care.
• Aphids can sometimes be a problem in early spring. The best solution is to blast them off your tree with a heavy stream of water. DO NOT use insecticidal soap – it can burn and defoliate trees.
• Japanese Maples grown in heavy clay soil or in a container may experience root rot. Symptoms of root rot are wilting (even though soil is moist) or dead branches that don’t leaf out in the spring. Root rot is caused by fungal organisms found in heavy, poorly aerated or waterlogged soil. To prevent, site your maple in the proper soil with the proper moisture. To alleviate symptoms, use a soil fungicide drench and foliar spray. Follow chemical directions PRECISELY!
• Japanese Maples planted in hot, very sunny locations with mid day sun may develop a leaf scorch, acondition that occurs when leaves transpire moisture faster than tree roots can absorb it from the soil. Prevent this ‘mostly cosmetic’ problem by planting in cooler, dappled shade away from drying summer wind. Keep soil moist but NOT WET, especially during dry periods. Keep water off of the foliage.
• Drought equals stress and Japanese Maples won’t tolerate much of either. Trees that don’t toleratedrought well can sometimes die ‘suddenly’ in the spring as they leaf out. This occurs because treesuse up all their carbohydrate reserves to break winter dormancy. After leafing out, food supplies areexhausted and the tree must draw on root reserves and roots moving water up to the tree. If rootshave died during drought the previous summer, they are not capable of supplying food and water, sothe tree dies. To prevent ‘sudden spring death’ of Japanese Maples, be sure that you keep trees evenlywatered during periods of drought.
LANDSCAPEJapanese Maples are great accents in a rock garden or in a mixed border. Upright growing specimen are best among taller plants.• Pair Japanese Maples with conifers to complement their lovely colors.• Japanese Maples are excellent understory trees. Tree roots are shallow and not overly competitive, sopair with similar rooted rhododendrons, azaleas, hosta and ferns.• Place cascading Japanese Maples varieties near low walls or at the edge of ponds.• Japanese Maples are excellent bonsai and container plants.