Acer is a genus of trees or shrubs commonly known as maple. There are approximately 128 species, most of which are native to Asia, with a number also appearing in Europe, northern Africa, and North America. Only one species, Acer laurinum, extends to the Southern Hemisphere. The type species of the genus is the sycamore maple, Acer pseudoplatanus, the most common maple species in Europe.
Most maples are trees growing to 10–45 m (33–148 ft) height. Others are shrubs less than 10 metres tall with a number of small trunks originating at ground level. Most species are deciduous, and many are renowned for their autumn leaf colour, but a few in southern Asia and the Mediterranean region are evergreen.
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. The distinctive fruit are called samaras, “maple keys”, “helicopters”, “whirlybirds” or “polynoses”. 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. People often call them “helicopters” due to the way that they spin as they fall.
Maples are important as source of syrup and wood. Dried wood is often used for the smoking of food. The Sugar maple (A. saccharum) is tapped for sap, which is then boiled to produce maple syrup or made into maple sugar or maple taffy. It takes about 40 litres (42 US qt) of sugar maple sap to make 1 litre (1.1 US qt) of syrup. While any Acer species may be tapped for syrup, many do not have sufficient quantities of sugar to be commercially useful. 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, pool cue shafts, and butcher’s blocks. Maple is also considered a tonewood, or a wood that carries sound waves well, and is used in numerous musical instruments. Maple is harder and has a brighter sound than mahogany, which is another major tonewood used in instrument manufacture. As Maple is 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.