It may be a red glow between city walls in autumn, a sparkle of apple green in spring, a sculpture to catch the snow in winter. It can provide a soft presence in a small front yard or command attention with wine-dark foliage against a backdrop of summer greens. It is the Japanese maple, and among small trees and shrubs for temperate climates, none is more versatile.
There are many maple species in Japan, but most of the trees that gardeners call Japanese maples are varieties of Acer palmatum, with some belonging to A. japonicum and A. shirasawanum. The natural range of A. palmatum includes not only Japan but parts of Korea, China, and Russia. The species can grow to 20 or 30 feet tall, often in the understory of open woods between larger trees. But it has been cultivated in Japanese gardens for centuries. Gardeners have taken advantage of the plant's natural genetic variation to select hundreds of distinct cultivars. "The range of leaf shape is pretty phenomenal," says Ben Chu, horticultural supervisor at Seiwa-En, the Japanese garden at the Missouri Botanical Garden in St. Louis.
Japanese maples are at their best in USDA Plant Hardiness Zones 6 through 8; a few are hardy as far north as Zone 4b. They do especially well in the moderate conditions of the Pacific Northwest. For colder climates, some types will grow in containers that can be moved to shelter in winter. In hotter areas, trees need consistent water and afternoon shade to thrive.
Plant a Japanese maple in early spring or before midautumn, but not in summer. Planting in early fall gives the tree time to put down new roots so that in spring, when the sap begins to rise, the tree can put energy into developing topgrowth. Water deeply at least once a week until the ground freezes. Japanese maples require consistent moisture, but an established tree is not likely to need fertilizing. They tolerate a wide range of soil pH, though slightly acidic soil is ideal. The one nonnegotiable requirement is good drainage. Especially in clay soil, it's wise to dig mulch or composted bark into a wide area that extends beyond the planting site. Then dig a wide planting hole that is no deeper than the root ball. If perennials or a groundcover will be planted beneath the tree, Chu advises planting them at the same time as the tree, in the soil beyond the root ball. That way, after the tree has reached out with its fibrous roots, the roots won't be disturbed by digging.
Many of the smaller Japanese maple varieties can be grown in containers. In fact, Don Mahoney, curator of plant collections at the San Francisco Botanical Garden in Golden Gate Park, figures he has 30 different varieties planted in pots in his confined city back yard.
He moves them into as much sun as he can in spring to help them develop their pigment; in the arid summertime, he moves them into the shade. "Fall color is very unusual on the West Coast," he says, "so after the hot spell, I move them out front and center where I can admire them."