maple

 

common name for the genus Acer of the Aceraceae, a family of deciduous trees and shrubs of the Northern Hemisphere, found mainly in temperate regions and on tropical mountain slopes. Acer, the principal genus, includes the many maples and the box elder. Maples are popular as shade trees and often have brilliantly colored foliage in the fall. Several E North American species provide valuable timber, notably the sugar, hard, or rock, maple (A. saccharum), and the more brittle-timbered black maple (A. nigrum). Their strong, close-grained, easily worked hardwood is used in shipbuilding and aircraft construction, for floors, fuel, and wood pulp, and in many other industries. Bird's-eye and curly maple are decorative cuts used for cabinetmaking. In addition, these two maples are the main sources of maple sugar. A prevalent and widely distributed North American species is the swamp, or red, maple (A. rubrum). The box elder, or ash-leaved maple (A. negundo), is a smaller North American species also planted as a shade tree; its softer wood is used for woodenware, cheap furniture, and paper pulp. Several European and Japanese maples have been introduced to the United States as ornamentals. The only other genus of the family is Dipteronia, consisting of two species indigenous to China. All members of the family have characteristic winged fruits. Maple syrup is the concentrated sap obtained for commercial purposes from the sugar maple and the black maple. Sap flows intermittently for periods of up to six weeks in the spring, is caught in buckets, strained, and concentrated by boiling to a density of 11 lb (4.9 kg) per gal for syrup or evaporated further for sugar. The syrup and sugar, first prepared by Native Americans (by dropping hot rocks into the sap or by freezing out the water) became the staple sweetening used by the colonists and remained important until c.1875. As cane sugar—with a higher saccharine content and a lower manufacturing cost—gained precedence and as the maple forest stands, or “sugar bush,” were depleted, maple sugar and syrup became scarcer and are now used mainly for confectionery and for flavoring, especially of tobacco. Vermont and New York are the chief producing states. Maples are classified in the division Magnoliophyta, class Magnoliopsida, order Sapindales, family Aceraceae.

Bibliography

See H. and S. Nearing, The Maple Sugar Book (1950, repr. 1970).

Maple
Acer pseudoplatanus (Sycamore Maple) foliage
Scientific classification
Kingdom: Plantae Phylum: Magnoliophyta Class: Magnoliopsida Order: Sapindales Family: Sapindaceae Genus: Acer L.
Distribution
Species
See List of Acer species

Trees or shrubs in the genus Acer are commonly called Maples. They are variously classified in a family of their own, the Aceraceae, or (together with the Hippocastanaceae) included in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group classification, favour inclusion in Sapindaceae. There are approximately 125 species, most of which are native to Asia, but several species also occur in Europe, northern Africa, and North America.

The word Acer is derived from a Latin word meaning "sharp" (referring to the characteristic points on the leaves) and was first applied to the genus by the French botanist Joseph Pitton de Tournefort in 1700. The type species of the genus is Acer pseudoplatanus (Sycamore Maple).^[1]

Morphology

Maples are mostly trees growing to 10-40 metres (30-130 ft) in height. Others are shrubs less than 10 metres tall with a number of small trunks originating at ground level. Most species are deciduous, but a few in southern Asia and the Mediterranean region are evergreen. Most are shade-tolerant when young, and are often late-successional in ecology; many of the smaller species are usually understory trees growing under the canopies of other larger trees, while the larger species eventually become dominant canopy trees. Maple root systems are typically dense and fibrous. A few species, notably Acer cappadocicum, frequently produce root sprouts, which can develop into clonal colonies.^[1]

Maples are distinguished by opposite leaf arrangement. The leaves in most species are palmate veined and lobed, with 3-9 (rarely to 13) veins each leading to a lobe, one of which is central or apical. A small number of species differ in having palmate compound, pinnate compound, pinnate veined or unlobed leaves. Several species, including Acer griseum (Paperbark Maple), Acer mandshuricum (Manchurian Maple), Acer maximowiczianum (Nikko Maple), and Acer triflorum (Three-flowered Maple), have trifoliate leaves. One species, Acer negundo (Manitoba Maple), has pinnately compound leaves that may be simply trifoliate or may have five, seven, or rarely nine leaflets. A few, such as Acer laevigatum and Acer carpinifolium (Hornbeam Maple), have pinnately-veined simple leaves.

The flowers are regular, pentamerous, and borne in racemes, corymbs, or umbels. They have four or five sepals, four or five petals about 1–6 mm long (absent in some species), four to ten stamens about 6-10 mm long, and two pistils or a pistil with two styles. The ovary is superior and has two carpels, whose wings elongate the flowers, making it easy to tell which flowers are female. Maples flower in late winter or early spring, in most species with or just after the leaves appear, but in some before them.^[2]

Maple flowers are green, yellow, orange or red. Though individually small, the effect of an entire tree in flower can be striking in several species. Some maples are an early spring source of pollen and nectar for bees.

The distinctive fruit are called samaras or "maple keys". These seeds occur in distinctive pairs each containing one seed enclosed in a "nutlet" attached to a flattened wing of fibrous, papery tissue. They are shaped to spin as they fall and to carry the seeds a considerable distance on the wind. Seed maturation is usually in a few weeks to six months after flowering, with seed dispersal shortly after maturity. Most species require stratification in order to germinate, and some seeds can remain dormant in the soil for several years before germinating.^[1]

The genus is subdivided by its morphology into a number of sections and subsections.^[3]

Pests and diseases

The leaves are used as a food plant for the larvae of a number of Lepidoptera species (see List of Lepidoptera which feed on Maples). Aphids are also very common sap-feeders on maples. In horticultural applications a dimethoate spray will solve this.

Maples are affected by a number of fungal diseases. Several are susceptible to Verticillium wilt caused by Verticillium species, which can cause significant local mortality. Sooty bark disease, caused by Cryptostroma species, can kill trees which are under stress due to drought. Death of maples can also be caused more rarely by Phytophthora root rot and Ganoderma root decay. Maple leaves in late summer and autumn are commonly disfigured by "tar spot" caused by Rhytisma species and mildew caused by Uncinula species, though these diseases do not usually have an adverse effect on the trees' long-term health.^[4]

Uses

Horticulture

Maples are planted as ornamental trees by homeowners, businesses and municipalities. Acer platanoides (Norway Maple) is especially popular as it is fast-growing and extremely cold-resistant, though is also an invasive species in some regions. Other maples, especially smaller or more unusual species, are popular as specimen trees.^[1]

Cultivars

Numerous maple cultivars have been selected for particular characteristics and can be propagated only by grafting. Acer palmatum (Japanese Maple) alone has over 1,000 cultivars, most selected in Japan, and many of them no longer propagated or not in cultivation in the western world. Some delicate cultivars are usually grown in pots and rarely reach heights of more than 50-100 cm.^[1]

Bonsai

Maples are a popular choice for the art of bonsai. Acer palmatum, Acer buergerianum (Trident Maple), Acer ginnala (Amur Maple), Acer campestre (Field Maple) and Montpellier Maple (A. monspessulanum) are popular choices and respond well to techniques that encourage leaf reduction and ramification, but most species can be used.^[1]

Collections

Maple collections, sometimes called aceretums, occupy space in many gardens and arboreta around the world including the "five great W's" in England: Wakehurst Place Garden, Westonbirt Arboretum, Windsor Great Park, Winkworth Arboretum and Wisley Garden. In the United States, the aceretum at the Harvard-owned Arnold Arboretum in Boston is especially notable. In the number of species and cultivars, the Esveld Aceretum in Boskoop, Netherlands is the largest in the world.^[1]

Tourism

Many maples have bright autumn foliage, and many countries have leaf-watching traditions. In Japan, the custom of viewing the changing colour of maples in the autumn is called "momijigari". Nikko and Kyoto are particularly favoured destinations for this activity.

The particularly spectacular fall colours of the Acer rubrum (Red Maple) are a major contributor to the seasonal landscape in southeastern Canada and in New England. Fall tourism is a boon to the economy of this region, especially in Vermont, New Hampshire and Western Massachusetts. In the American Pacific Northwest, it is the spectacular fall colours of Acer circinatum (Vine Maple) that draw tourists and photographers.

Commercial uses

Maples are important as source of syrup and wood. Dried wood is often used for the smoking of food. They are also cultivated as ornamental plants and have benefits for tourism and agriculture.

Maple syrup

Further information: Maple Syrup

The Sugar Maple (Acer saccharum) is tapped for sap, which is then boiled to produce maple syrup or made into maple sugar or maple candy. It takes about 40 gallons of Sugar Maple sap to make a gallon of syrup. Syrup can be made from closely-related species as well, but their output is inferior. Sugar maples typically have a lifespan of 300 years.

Timber

Some of the larger maple species have valuable timber, particularly Sugar Maple in North America, and Sycamore Maple in Europe. Sugar Maple wood, often known as "hard maple", is the wood of choice for bowling pins, bowling alley lanes, drums and butcher's blocks. Maple wood is also used for the production of wooden baseball bats, though less often than ash or hickory.

Some maple wood has a highly decorative wood grain, known as flame maple and quilt maple. This condition occurs randomly in individual trees of several species, and often cannot be detected until the wood has been sawn, though it is sometimes visible in the standing tree as a rippled pattern in the bark.

Maple is considered a tonewood, or a wood that carries sound waves well, and is used in numerous musical instruments such as guitars and drums. It provides resonance and a lighter weight than many other woods used in necks such as rosewood. Also the look of a maple neck is appealing to many guitar players. Maple is also used to make bassoons.

Agriculture

As they are a major source of pollen in early spring before many other plants have flowered, maples are important to the survival of honeybees that play a commercially-important role later in the spring and summer.

Symbolism

The flag of Canada depicts a stylized maple leaf and is a prominent national symbol. In the United States, the maple has been adopted by New York,^[5] Vermont,^[6] Wisconsin^[7] and West Virginia.^[8] The Red Maple was adopted by Rhode Island ^[9]as their official state tree.

Acer cappadocicum (Cappadocian Maple)	Acer carpinifolium leaves	Acer griseum compound (trifoliate) leaf	Acer macrophyllum flowers and young leaves
Acer laevigatum leaves and fruit	Acer sempervirens foliage	Acer ginnala foliage	Acer rubrum trees in autumn
Acer palmatum trees and bamboo in Japan	Acer grandidentatum in autumn colour	Acer platanoides leaf	Acer palmatum leaf in autum

References

hsb:Klonnds-nl:Plataan (Acer)

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