Acer

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Acer

Maples
Acer-saccharinum-leaves-e.jpg
Genus: Acer
Family: Sapindaceae
Type: Trees and shrubs

Maples are trees or shrubs in the genus Acer. There are approximately 125 species, most of which are native to Asia, but several species also occur in Europe, northern Africa, and North America. Maples 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, favor inclusion in Sapindaceae.

The word Acer is derived from a Greek 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.[1]

Description[edit]

Maples are mostly trees growing to 10-40 m (30-130 feet) in height. Others are shrubs less than 10 m 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.

Maples are distinguished by opposite leaf arrangement. The leaves in most species are palmately veined and lobed, with 3-9 veins each leading to a lobe, one of which is in the middle. A small number of species differ in having palmate compound, pinnate compound, pinnate veined or unlobed leaves.

Several species, including the Paperbark Maple (Acer griseum), Manchurian Maple (Acer mandshuricum), Nikko Maple (Acer maximowiczianum), and Three-flowered Maple (Acer triflorum), have trifoliate leaves. One species, the Boxelder (Acer negundo), has pinnately compound leaves that may be simply trifoliate or may have five, seven, or rarely nine leaflets. The Hornbeam Maple (Acer carpinifolium), has pinnately-veined simple leaves that resemble those of hornbeams (Carpinus spp.).

Red Maple (Acer rubrum) flowers

The flowers are regular, pentamerous, and borne in racemes, corymbs, or umbels. They have five sepals, five petals about 1 to 6 mm long, 12 stamens about 6-10 mm long in two rings of six, 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.


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 of 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]

Most maples freate extensive but shallow root systems, and tend to create very dry shade near the tree, so underplanting can be difficult.

Ecology[edit]

Maples tend to grow both as pioneer species and as subcanopies to larger trees. Most cast very dense shade, limiting undergrowth and underplanting.

Culture and Use[edit]

Horticulture[edit]

Acer palmatum has over 1,000 cultivars. This cultivar is A. palmatum 'Sango kaku', sometimes called "coralbark maple".

Maples are planted as ornamental or shade trees by homeowners, businesses and municipalities. The Norway Maple (Acer platanoides) 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 that have been selected for particular characteristics are usually propagated by grafting. Japanese Maple (Acer palmatum) alone has over 1,000 cultivars, most of which were selected in Japan.[1] Some delicate cultivars are usually grown in pots and rarely reach heights of more than 50-100 cm.

Bonsai

Maples are a popular choice for the art of bonsai. Japanese Maple, Trident Maple (Acer buergerianum), Amur Maple (Acer ginnala), Field Maple (Acer campestre) and Montpellier Maple (Acer 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 University-owned Arnold Arboretum in Boston, Massachusetts is especially notable. In the number of species and cultivars, the Esveld Aceretum in Boskoop, Netherlands is the largest in the world.[1]

Commercial uses[edit]

Maples are important as source of syrup and wood. 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. Syrup can be made from closely-related species as well, but their output is inferior.

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 instruments such as guitar and the drums.

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.

Pests, Diseases, and other Problems[edit]

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 Rhystima species and Powdery Mildew caused by Uncinula species, though these diseases do not usually have an adverse effect on the trees' long-term health.[2]

Aphids:

Scale Insects:

Hoppers

Psyllids

Whiteflies

Mealybugs

Bugs

Thrips

Flies

Beetles:

Weevils

Caterpillars:

Wasps

Mites

References[edit]

  • Britton, Nathaniel Lord; Addison Brown (1913). An Illustrated Flora of the Northern United States and Canada, Volume 1 (second edition ed.). Dover Publications, inc.. pp. 494-498. 
  • Ann Fowler Rhoads and Timothy A. Block (2000). The Plants of Pennsylvania: An Illustrated Manual. Anna Anisko, illustrator. Morris Arboretum, University of Pennsylvania Press. pp. 118-123. 
  • Pirone, Pascal P.. Diseases & Pests of Ornamental Plants. pp. 109-117. 
  • Cranshaw, Whitney (2004). Garden Insects of North America. Princeton University Press. pp. 577-578. 
  1. a b c d e f van Gelderen, C.J. & van Gelderen, D.M. (1999). Maples for Gardens: A Color Encyclopedia
  2. Phillips, D. H. & Burdekin, D. A. (1992). Diseases of Forest and Ornamental Trees. Macmillan. ISBN 0-333-49493-8.