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Acer saccharum (sugar maple) is a species of maple native to the hardwood forests of northeastern North America, from Nova Scotia west to southern Ontario, and south to Georgia and Texas. Sugar maple is best known for its bright fall foliage and for being the primary source of maple syrup.
The leaves are deciduous, up to 20 cm (7.9 in) long and equally wide, with five palmate lobes. The basal lobes are relatively small, while the upper lobes are larger and deeply notched. In contrast with the angular notching of the silver maple, however, the notches tend to be rounded at their interior. The fall color is often spectacular, ranging from bright yellow through orange to fluorescent red-orange. Sugar maples also have a tendency to color unevenly in fall. In some trees, all colors above can be seen at the same time. They also share a tendency with red maples for certain parts of a mature tree to change color weeks ahead of or behind the remainder of the tree. The leaf buds are pointy and brown-colored. The recent year's growth twigs are green, and turn dark brown.
The flowers are in corymbs of five to 10 together, yellow-green and without petals; flowering occurs in early spring after 30-55 growing degree days. The fruit is a double samara with two winged seeds, the seeds are globose, 7–10 mm (0.28–0.39 in) in diameter, the wing 2–3 cm (0.79–1.2 in) long. The seeds fall from the tree in autumn, where they must be exposed to 90 days of sub-40°F temperatures to break their coating down. Germination of A. saccharum is slow, not taking place until the following spring when the soil has warmed and all frost danger is past.
It is closely related to the black maple, which is sometimes included in this species, but sometimes separated as Acer nigrum. The western American bigtooth maple (Acer grandidentatum) is also treated as a variety or subspecies of sugar maple by some botanists.
The sugar maple is also often confused with the Norway maple, though they are not closely related within the genus. The sugar maple is most easily identified by clear sap in the leaf petiole (the Norway maple has white sap), brown, sharp-tipped buds (the Norway maple has blunt, green or reddish-purple buds), and shaggy bark on older trees (the Norway maple bark has small grooves). Also, the leaf lobes of the sugar maple have a more triangular shape, in contrast to the squarish lobes of the Norway maple.
Although many people think a red sugar maple leaf is featured on the flag of Canada, the official maple leaf does not belong to any particular maple tree. Instead, it was specially designed to be as identifiable as possible on a flag waving in the wind.
The sugar maple is an extremely important species to the ecology of many forests in North America. Pure stands are common, and it is a major component of the northern and central U.S. hardwood forests. In the north, it forms associations of beech-maple and sugar maple-yellow birch, which is most important beyond the northern limit of beech. Sugar maple-American basswood, sugar maple-white ash and sugar maple-ironwood--red oak are also common forest associations.
Sugar maple is among the most shade tolerant of large deciduous trees. Among North American maples, its shade tolerance is exceeded only by the striped maple, a smaller tree. Like other maples, its shade tolerance is manifested in its ability to germinate and persist under a closed canopy as an understory plant, and respond with rapid growth to the increased light formed by a gap in the canopy. The sugar maple can grow comfortably in any type of soil, except sand.
Sugar maples engage in hydraulic lift, drawing water from lower soil layers and exuding that water into upper, drier soil layers. This not only benefits the tree itself, but also many other plants growing around it.
Human influences have contributed to the decline of the sugar maple in many regions. Its role as a species of mature forests has led it to be replaced by more opportunistic species in areas where forests are cut over. The sugar maple also exhibits a greater susceptibility to pollution than other species of maple. Acid rain and soil acidification are some of the primary contributing factors to maple decline. Also, the increased use of salt over the last several decades on streets and roads for deicing purposes has decimated the sugar maple's role as a "street-front" tree.
In some parts of eastern North America, particularly near urbanized areas, the sugar maple is being displaced by the Norway maple. The Norway maple is also highly shade tolerant, but is considerably more tolerant of urban conditions, resulting in the sugar maple's replacement in those areas heavily disturbed by human activities. In addition, Norway maple produces much larger crops of seeds, allowing it to out-compete native species.
Cultivation and uses 
The sugar maple is one of the most important Canadian trees, being, with the black maple, the major source of sap for making maple syrup. Other maple species can be used as a sap source for maple syrup, but some have lower sugar contents and/or produce more cloudy syrup than these two.
The wood is one of the hardest and densest of the maples, 740 kg/m3 (46 lb/cu ft), and is prized for furniture and flooring. The sapwood can be white in color, and smaller logs may have a higher proportion of this desirable wood. Bowling alleys and bowling pins are both commonly manufactured from sugar maple. Trees with wavy woodgrain, which can occur in curly, quilted, and "birdseye maple" forms, are especially valued. Maple is also the wood used for basketball courts, including the floors used by the NBA, and it is a popular wood for baseball bats, along with white ash. It is also widely used in the manufacture of musical instruments, such as the members of the violin family (sides and back), guitars (neck), and drum shells. It is also quite flexible and makes excellent archery bows.
Canadian maple, often referred to as "Canadian hardrock maple", is prized for pool cues, especially pool cue shafts, and the highest grades of this white wood are used by virtually all (both production line and custom hand-made) cue makers to make high-quality shafts. Some production-line cues will use lower-quality Canadian maple wood with cosmetic issues, such as "sugar marks", which are (most often) light brown discolorations visible on the shaft caused by sap in the wood. Great shaft wood has a very consistent grain, and no marks or discoloration. Sugar marks usually do not affect how the cue plays, but are not as high quality as those without it. This wood is also used in skateboard decks for its strength.
The sugar maple was a favorite street and park tree during the 19th century because it was easy to propagate and transplant, is fairly fast-growing, and has beautiful fall color. As noted above however, it proved too delicate to continue in that role after the rise of automobile-induced pollution and was replaced by Acer Platanoides and other hardier species. The shade and the shallow, fibrous roots may interfere with grass growing under the trees. Deep, well-drained loam is the best rooting medium, although sugar maples can grow well on sandy soil which does not become excessively dry. Light (or loose) clay soils are also well known to support sugar maple growth. Poorly drained areas are unsuitable, and the species is especially short-lived on flood-prone clay flats. Its salt tolerance is low and it is very sensitive to boron.
- 'Apollo' - columnar
- 'Arrowhead' - pyramidal crown
- 'Astis' ('Steeple') - heat-tolerant, good in southeastern USA, oval crown
- 'Bonfire' - fast growing
- 'Caddo' - naturally occurring southern ecotype, great drought and heat tolerance, good choice for the Great Plains region
- 'Columnare' ('Newton Sentry') - very narrow
- 'Fall Fiesta' - tough-leaved, colorful in season, above-average hardiness
- 'Goldspire' - columnar with yellow-orange fall color
- 'Green Mountain' (PNI 0285) - durable foliage resists heat and drought, oval crown, very hardy (cold tolerance may match 'Unity')
- 'Legacy' - tough, vigorous and popular
- 'Monumentale' - columnar
- 'Sweet Shadow' - lacy foliage
- 'Temple's Upright' - almost as narrow as 'Columnare'
- 'Unity' - one of hardiest cultivars, from Manitoba
In popular culture 
The sugar maple is depicted on the state quarter of Vermont, issued in 2001.
See also 
- The Comfort Maple, Pelham, Ontario
- Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 [and more or less continuously updated since]. mobot.org
- Germplasm Resources Information Network: Acer saccharum
- Northern Ontario Plant Database: Acer saccharum
- Oklahoma Biological Survey: Acer saccharum
- "GSMNP tall trees". Nativetreesociety.org. Retrieved 2011-03-03.
- Lawrence O. Copeland; M. B. McDonald (31 October 2001). Principles of seed science and technology. Springer. pp. 194–. ISBN 978-0-7923-7322-3. Retrieved 25 September 2010
- "Hydraulic lift and its influence on the water content of the rhizosphere: an example from sugar maple, Acer saccharum". Springerlink.com. Retrieved 2011-03-03.
- Heilingmann, Randall B. "Hobby Maple Syrup Production (F-36-02)". Ohio State University.
- Hard Maple published by Niche Timbers
- Daniel L. Cassens. "Hard or sugar maple". Purdue University:Purdue Extension.
- Horton, J. L.; Hart, S.C. (1998). "Hydraulic lift: a potentially important ecosystem process". Trends in Ecology and Evolution 13 (6): 232–235. doi:10.1016/S0169-5347(98)01328-7. PMID 21238277.
- Canham, C. D. (1989). "Different Respones to Gaps Among Shade-Tolerant Tree Species". Ecology 70 (3): 548–550. doi:10.2307/1940200.
- Brisson, J., Bergeron, Y., Bouchard, A., & Leduc, A. (1994). Beech-maple dynamics in an old-growth forest in southern Quebec, Canada. Ecoscience (Sainte-Foy) 1 (1): 40-46.
- Duchesne, L.; Ouimet, R.; Houle, D. (2002). "Basal Area Growth of Sugar Maple in Relation to Acid Deposition, Stand Health, and Soil Nutrients". Journal of Environmental Quality 31 (5): 1676–1683. doi:10.2134/jeq2002.1676. PMID 12371186.
Further reading 
- Melvyn Tyree. "Maple sap exudation: How it happens" (PDF). Maple Syrup Journal 4 (1): 10–11.
- Damián Cirelli, Richard Jagels, and Melvin T. Tyree (2008). "Toward an improved model of maple sap exudation: the location and role of osmotic barriers in sugar maple, butternut and white birch" (PDF). Tree Physiology (Victoria, Canada: Heron Publishing) 28 (8): 1145–1155. PMID 18519246.
|Wikimedia Commons has media related to: Acer saccharum|
- UI Plants: Woody Ornamentals (sugar maple)
- USDA Plants Profile: Acer saccharum
- Acer saccharum in Godman, Yawney and Tubbs. US Forest Service Silvics Manual
- Acer saccharum at Ohio State Horticulture & Crop Sciences
- Acer saccharum images at bioimages.vanderbilt.edu
- Winter ID Pictures
- Historic Photos and Technical Reports Documenting Sugar Maple Research, from digital archives at the University of Vermont.
- Interactive Distribution Map for Acer saccharum
- Xycol : Acer saccharum Marshall subsp. saccharum (in French)