Japanese Maple

Appearance

"Acer palmatum" is a deciduous shrub or small tree reaching heights of 6 to 10 m, rarely 16 metres, often growing as an understory plant in shady woodlands. It may have multiple trunks joining close to the ground. In habit, it is often shaped like a hemisphere or takes on a dome-like form, especially when mature. The leaves are 4–12 cm 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 2–3 cm long with a 6–8 mm seed. The seeds of Japanese maple 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 colour.

Three subspecies are recognised:
⤷ "Acer palmatum" subsp. "palmatum". Leaves small, 4–7 cm wide, with five or seven lobes and double-serrate margins; seed wings 10–15 mm. Lower altitudes throughout central and southern Japan.
⤷ "Acer palmatum" subsp. "amoenum" H.Hara. Leaves larger, 6–12 cm wide, with seven or nine lobes and single-serrate margins; seed wings 20–25 mm. Higher altitudes throughout Japan and South Korea.
⤷ "Acer palmatum" subsp. "matsumurae" Koidz. Leaves larger, 6–12 cm wide, with seven lobes and double-serrate margins; seed wings 15–25 mm. Higher altitudes throughout Japan.

Naming

The term "Japanese Maple" is also sometimes used to describe other species within series "Palmata" that are similar to "A. palmatum" and are native to China, Korea or Japan including:
⤷ "Acer duplicatoserratum"
⤷ "Acer japonicum"—Downy Japanese Maple
⤷ "Acer pseudosieboldianum"—Korean Maple
⤷ "Acer shirasawanum"—Fullmoon Maple
⤷ "Acer sieboldianum"—Siebold's Maple

Given that these maples are phenotypically variable within each species, and may hybridise with one another, distinguishing between them may be a matter of gradient speciation. In commercial propagation, "A. palmatum" is often used as rootstock for these other species.

Uses

Japanese Maple has been cultivated in Japan for centuries and in temperate areas around the world since the 1800s. The first specimen of the tree reached England in 1820.

When Swedish doctor-botanist Carl Peter Thunberg traveled in Japan late in the eighteenth century, he secreted out drawings of a small tree that would eventually become synonymous with the high art of oriental gardens....hieroglyph snipped... 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.

For centuries Japanese horticulturalists have 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 currently available commercially and are a popular item at garden centres and other retail stores in Europe and North America. Red-leafed cultivars are the most popular, followed by cascading green shrubs with deeply dissected leaves.

Preparations from the branches and leaves are used as a treatment in traditional Chinese medicine.