Acer palmatum, commonly known as听Japanese maple,听palmate maple,听or听smooth Japanese maple听(Japanese:听irohamomiji,听銈ゃ儹銉忋儮銉熴偢, or听momiji, (鏍�), is a species of woody plant native to听,听,听, eastern听, and southeast听.听Many different听听of this听听have been selected and they are grown worldwide for their large variety of attractive forms, leaf shapes, and spectacular colors.
Description
Acer palmatum听is听, with the growth habit of a听听or small听听reaching heights of 6 to 10听m (20 to 33听ft), rarely 16听m (52听ft), reaching a mature width of 4.5 to 10听m (15 to 33听ft),听often growing as an understory plant in shady听. It may have multiple trunks joining close to the ground. In听, its canopy often takes on a听-like form, especially when mature.听The听听are听4鈥�12听cm (1+1鈦�2鈥�4+3鈦�4听in) long and wide, palmately lobed with five, seven, or nine acutely pointed lobes. The听听are produced in small听, the individual flowers with five red or purple sepals and five whitish petals. The听听is a pair of winged听, each samara听2鈥�3听cm (3鈦�4鈥�1+1鈦�4听in) long with a听6鈥�8听mm (1鈦�4鈥�5鈦�16听in) seed. The seeds of听Acer palmatum听and similar听听require听听in order to听.
Even in nature,听Acer palmatum听displays considerable听, with听听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听听are recognised:
- Acer palmatum听subsp.听palmatum. Leaves small,听4鈥�7听cm (1+1鈦�2鈥�2+3鈦�4听in) wide, with five or seven lobes and double-serrate margins; seed wings听10鈥�15听mm (3鈦�8鈥�5鈦�8听in). Lower altitudes throughout central and southern Japan (not听).
- Acer palmatum听subsp.听amoenum听(Carri猫re) H.Hara. Leaves larger,听6鈥�12听cm (2+1鈦�4鈥�4+3鈦�4听in) wide, with seven or nine lobes and single-serrate margins; seed wings听20鈥�25听mm (3鈦�4鈥�1听in). Higher altitudes throughout Japan and South Korea.
- Acer palmatum听subsp.听matsumurae听Koidz. Leaves larger,听6鈥�12听cm (2+1鈦�4鈥�4+3鈦�4听in) wide, with seven (rarely five or nine) lobes and double-serrate margins; seed wings听15鈥�25听mm (5鈦�8鈥�1听in). Higher altitudes throughout Japan.
Cultivation and uses
Acer palmatum听has been cultivated in Japan for centuries and in听听areas around the world since the 1800s.听The first specimen of the tree reached Britain in 1821.
When Swedish doctor-botanist听听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.听He gave it the species name听palmatum听after the hand-like shape of its leaves, similar to the centuries-old Japanese names听kaede听and听momiji, references to the 'hands' of frogs听and babies,[]听respectively.
Japanese horticulturalists have long developed听听from maples found in Japan and nearby Korea and China. They are a popular choice for听听enthusiasts and have long been a subject in art.
Numerous cultivars are popular in听听and听, with red-leafed favored, followed by cascading green shrubs with deeply dissected leaves.
Acer palmatum听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听1鈦�2听to 82听ft), depending on type.
Preparations from the branches and leaves are used as a treatment in traditional Chinese medicine.
Growing conditions
In their natural habitat, they grow in the understory; most cultivars prefer part shade, especially in hotter climates, but they will also grow in heavy shade. Some cultivars will tolerate full sun, more so at higher latitudes and less at lower latitudes; red, purple-red, black-red, bronze, and some dark green cultivars are generally more full sun tolerant. Variegated white, cream, yellow, yellow-orange, or light green cultivars mostly require shade protection. Almost all are adaptable and blend well with听. The trees are particularly suitable for borders and ornamental paths because the root systems are compact and not invasive. Many varieties of听Acer palmatum听are successfully grown in containers.听Trees are prone to die during periods of drought and prefer consistent water conditions; more established trees are less prone to drought. They benefit from being mulched yearly with a 2" layer of aged organic matter mulch, covering at least beyond the entire drip-line of the tree, but not allowed to touch the bark at the base of the tree. Moderate to well-drained soil is essential as they will not survive in poorly drained waterlogged soil. Trees do not require or appreciate heavy fertilization and should only be very lightly fertilized, preferably using polymer-coated slow-release fertilizer with a 3 to 1 ratio of nitrogen to phosphorus respectively, or preferably a bio-solid based fertilizer like a 6-4-0 N-P-K. High Nitrogen lawn fertilizer should be avoided in the immediate vicinity of these trees, as excessive nitrogen can cause overly vigorous growth that is not consistent with the natural form of the tree, and is prone to dieback and pathogens.[]
Japanese maples are best to grow in hardiness zones 5-8.
Pruning
If space is not a constraint, no pruning is necessary except to remove any dead branches. Trees naturally self-prune foliage that doesn't receive enough light, such as internal branches which are overly shaded by its own canopy. Some growers prefer to shape their trees artistically or to thin out interior branches to better expose the graceful main branches. The form of the tree, especially without leaves in winter, can be of great interest and can be pruned to highlight this feature. Trees heal readily after pruning without needing aftercare. This species should not be pruned like a hedge, but instead methodically shaped by carefully choosing individual branches to remove. They can also be pruned just to maintain a smaller size to suit a particular location.听Acer palmatum听can also be used as听.[]
Cultivars
Over 1,000听听have been chosen for particular characteristics, which are听听by asexual reproduction most often by听, but some cultivars can also be propagated by听,听,听, or听. Some cultivars are not in cultivation in the听听or have been lost over the generations, but many new cultivars are developed each decade.听Cultivars are chosen for听听aspects such as leaf shape and size (shallowly to deeply lobed, some also palmately compound), leaf color (ranging from chartreuse through dark green or from orange to red, to dark purple, others听听with various patterns of white and pink), bark texture and color, and growth pattern. Most cultivars are less vigorous and smaller than is typical for the species, but are more interesting than the relatively mundane species. Cultivars come in a large variety of forms including upright, broom, vase, umbrella, weeping, cascading, dwarf, shrub, and ground cover. Most cultivars are听听from seedlings of open-pollinated plants, purposeful breeding is not common, and less often from grafts of听.
In Japan,听iromomiji听is used as an accent tree in Japanese gardens, providing gentle shade next to the house in the summer and beautiful colors in autumn. Many cultivars have characteristics that come into prominence during different seasons, including the color of new or mature leaves, extraordinary autumn color, color and shape of samaras, or even bark that becomes more brightly colored during the winter. Some cultivars can scarcely be distinguished from others unless labeled. In some cases, identical cultivars go by different names, while in other cases, different cultivars may be given the same name.[]
