Technically, the term "Japanese maple tree" applies to any maple species endemic to Japan. In the context of gardening in the western world, Japanese maple trees constitute the species Acer palmatum and its numerous cultivars. These trees reach mature heights of 6 to 50 feet, depending on the type, and bear ornamental foliage in shades of red and purple-red. The lifespan of a Japanese maple tree depends heavily on the circumstances in which it lives and may vary wildly.
Japanese Maple Lifespan
Japanese maple trees grow slowly. It can take 50 years for a tree, growing at a rate of 1 foot per year, to reach its full mature height. In Japan, wild Japanese maples continue to grow until age 100. Resources such as the book "Japanese Maples: Momiji and Kaede" do not place lifespan estimates on the trees, as extenuating circumstances affect tree lifespan enough to make estimates unrealistic. Arborist Tom Mugridge writes that a 50-year-old Japanese maple may "have many more years of life," while the aforementioned book on Japanese maples makes reference to trees older than 100 years old. Maple trees in general may live for longer than 200 years.
Factors Affecting Lifespan
Numerous factors heavily impact the potential lifespan of a Japanese maple tree, among them culture and potential pests and diseases. Culture entails all the conditions in which a tree grows. Japanese maple trees require partial sun or partial shade exposure to flourish. Though trees tolerate shady conditions, full sun exposure may lessen a tree's lifespan. Japanese maples tolerate a number of soil conditions though only have moderate drought tolerance. Trees do not tolerate flooding or standing water in soil -- flooding may kill trees or significantly lessen lifespan. Japanese maples flourish in acidic, well-drained and fertile soil. Organic materials such as compost and mulch increase soil fertility, as do all-purpose garden fertilizers. Always use fertilizers exactly as instructed.
Pests and Diseases
Japanese maple trees experience problems with many fungal diseases, including Anthracnose, Verticillium Wilt and various wood rots and decays. The most efficient manner of increasing Japanese maple lifespan entails preventing these diseases through precautionary measures such as soil testing and the maintenance of proper culture. Planting trees far enough from other plants to encourage air circulation helps prevent disease, as does minimizing dampness and moisture on foliage.
Japanese maples show a relatively high resistance to pests, though may suffer from Japanese beetle or spider mite infestations. The United States Department of Agriculture recommends using an integrated approach to managing such pests. Management methods include introducing predators, planting species resistant to pest infestation and applying pesticides.
Pruning Japanese Maple
Pruning a Japanese maple tree properly helps improve tree longevity, while improper pruning methods may impede longevity. In "Fine Gardening" magazine, author Cass Turnbull writes that Japanese maples develop unsightly, whip-like branches before they reach the age of 15. Many gardeners prune this growth out of impatience, though doing so makes the plant vulnerable to diseases and impedes the natural growth process, thus decreasing plant longevity. Restricting the height of Japanese maple doesn't work -- those who prune the tops of plants risk creating strange growth that affects a plant's lifespan. Rather than pruning for size, select a cultivar that grows to the size you need for the garden.
Pruning techniques other than these help plants achieve a healthy shape and symmetry. Pruning dead or dying growth helps unburden the tree and redirect nutrients and water to healthy parts of the plant, thus improving longevity.