Acer palmatum, commonly known as Japanese maple, palmate maple, or smooth Japanese maple (Japanese: irohamomiji, , or momiji, (栴), is a species of woody plant native to Japan, Korea, China, eastern Mongolia, and southeast Russia. Many different cultivars of this maple have been selected and they are grown worldwide for their large variety of attractive forms, leaf shapes, and spectacular colors.
Description
Acer palmatum is deciduous, with the growth habit of a shrub or small tree reaching heights of , rarely , reaching a mature width of , often growing as an understory plant in shady woodlands. It may have multiple trunks joining close to the ground. In habit, its canopy often takes on a dome-like form, especially when mature. The leaves are long and wide, palmately lobed with five, seven, or nine acutely pointed lobes. The flowers are produced in small cymes, the individual flowers with five red or purple sepals and five whitish petals. The fruit is a pair of winged samaras, each samara long with a seed. The seeds of Acer palmatum and similar species require stratification in order to germinate.
Even in nature, Acer palmatum displays considerable genetic variation, with seedlings from the same parent tree typically showing differences in such traits as leaf size, shape, and color. The overall form of the tree can vary from upright to weeping.
Three subspecies are recognised: Acer palmatum subsp. palmatum. Leaves small, wide, with five or seven lobes and double-serrate margins; seed wings . Lower altitudes throughout central and southern Japan (not Hokkaido). Acer palmatum subsp. amoenum . Leaves larger, wide, with seven or nine lobes and single-serrate margins; seed wings . Higher altitudes throughout Japan and South Korea. Acer palmatum subsp. matsumurae . Leaves larger, wide, with seven (rarely five or nine) lobes and double-serrate margins; seed wings . Higher altitudes throughout Japan.
Cultivation and uses
Acer palmatum has been cultivated in Japan for centuries and in temperate areas around the world since the 1800s. The first specimen of the tree reached Britain in 1821.
When Swedish doctor-botanist Carl Peter Thunberg traveled in Japan late in the eighteenth century, he produced drawings of a small tree that would eventually become synonymous with the high art of oriental gardens. He gave it the species name palmatum after the hand-like shape of its leaves, similar to the centuries-old Japanese names kaede and momiji, references to the 'hands' of frogs and babies, respectively.
Japanese horticulturalists have long developed cultivars from maples found in Japan and nearby Korea and China. They are a popular choice for bonsai enthusiasts and have long been a subject in art.
Numerous cultivars are popular in Europe and North America, with red-leafed favored, followed by cascading green shrubs with deeply dissected leaves.
Acer palmatum includes thousands of named cultivars with a variety of forms, colors, leaf types, sizes, and preferred growing conditions. Heights of mature specimens range from 0.5 to 25 m (1 1⁄2 to 82 ft), depending on type.
Preparations from the branches and leaves are used as a treatment in traditional Chinese medicine.