RED MAPLE (Acer rubrum)
Acer rubrum (Red Maple, also known as Swamp, Water or Soft Maple), is one of the most common and widespread deciduous trees of eastern North America. The U.S. Forest service recognizes it as the most common variety of tree in America. The red maple ranges from southeastern Manitoba around the Lake of the Woods on the border with Ontario and Minnesota, east to Newfoundland, south to Florida, and southwest to east Texas. Many of its features, especially its leaves, are quite variable in form. At maturity it often attains a height of around 15 m (49 ft). It is aptly named as its flowers, petioles, twigs and seeds are all red to varying degrees. Among these features, however, it is best known for its brilliant deep scarlet foliage in autumn.
Over most of its range, red maple is adaptable to a very wide range of site conditions, perhaps more so than any other tree in eastern North America. It can be found growing in swamps, on poor dry soils, and most anywhere in between. It grows well from sea level to about 900 m (3,000 ft). Due to its attractive fall foliage and pleasing form, it is often used as a shade tree for landscapes. It is used commercially on a small scale for maple syrup production as well as for its medium to high quality lumber. It is also the State Tree of Rhode Island. The red maple can be considered weedy or invasive. It is taking over forests in the eastern US, replacing traditional mainstays like oaks, as well as hickories and pines.
Though A. rubrum is usually easy to identify, it is highly changeable in morphological characteristics. It is a medium to large sized tree, reaching heights of 18 to 27 metres (59 to 89 ft) and exceptionally over 35 metres (115 feet). The leaves are usually 9 to 11 centimetres (3.5 to 4.3 in) long on a full grown tree. The trunk diameter can range from 46 to 76 cm (18 to 30 in), depending on the growing conditions. Its spread is about 12 m (39 ft). A 10-year-old sapling will stand about 6 m (20 ft) tall. In forests, the bark will remain free of branches until some distance up the tree. Individuals grown in the open are shorter and thicker with a more rounded crown. Generally speaking, however, the crown is irregularly ovoid with ascending whip-like curved shoots. The bark is a pale grey and smooth when the individual is young. As the tree grows the bark becomes darker and cracks into slightly raised long plates. The largest known living red maple is located near Armada, Michigan, at a height of 38.1 m (125 ft) and a bole circumference, at breast height, of 4.95 m (16.2 ft).
The leaves of the red maple offer the easiest way to distinguish it from its relatives. As with nearly all maple trees, they are deciduous and arranged oppositely on the twig. They are typically 5–10 cm (2.0–3.9 in) long and wide with 3-5 palmate lobes with a serrated margin. The sinuses are typically narrow, but the leaves can exhibit considerable variation. When 5 lobes are present, the three at the terminal end are larger than the other two near the base. In contrast, the leaves of the related silver maple, A. saccharinum, are much more deeply lobed, more sharply toothed and characteristically have 5 lobes. The upper side of A. rubrum’s leaf is light green and the underside is whitish and can be either glaucous or hairy. The leaf stalks are usually red and are up to 10 cm (3.9 in) long. Furthermore, the leaves can turn a brilliant red in autumn, but can also become yellow or orange on some individuals.
The twigs of the red maple are reddish in color and somewhat shiny with small lenticels. Dwarf shoots are present on many branches. The buds are usually blunt and greenish to reddish in color, generally with several loose scales. The lateral buds are slightly stalked, and in addition there may be collateral buds present as well. The buds form in fall and winter and are often visible from a distance due to their reddish tint. The leaf scars on the twig are V-shaped and contain 3 bundle scars.
The flowers are generally unisexual, with male and female flowers appearing in separate sessile clusters, though they are sometimes also bisexual. They appear in spring from April to May (though as early as late January in the southern part of its range), usually coming before the leaves. The tree itself is considered Polygamodioecious, meaning some individuals are male, some female, and some monoecious. The red maple will begin blooming when it is about 8 years old, but it significantly varies between tree to tree: some trees may begin flowering when they are 4 years old. The flowers are red with 5 small petals and a 5-lobed calyx borne in hanging clusters, usually at the twig tips. They are lineal to oblong in shape and are pubescent. The pistillate flowers have one pistil formed from two fused carpels with a glabrous superior ovary and two long styles that protrude beyond the perianth. The staminate flowers contain between 4 and 12 stamens, often with 8.
The fruit is a 15 to 25 millimeter (.5 to .75 inch) long double samara with somewhat divergent wings at an angle of 50 to 60 degrees. They are borne on long slender stems and are variable in color from light brown to reddish. They ripen from April through early June, before even the leaf development is altogether complete. After they reach maturity, the seeds are dispersed for a 1 to 2 week period from April through July.
Distribution and habitat
- rubrum is one of the most abundant and widespread trees in eastern North America. It can be found from the south of Newfoundland, Nova Scotia and southern Quebec to the south west of Ontario, extreme southeastern Manitoba and northern Minnesota; south to Wisconsin, Illinois, Missouri, eastern Oklahoma, and eastern Texas in its western range; and east to Florida. It has the largest continuous range along the North American Atlantic Coast of any tree that occurs in Florida. In total it ranges 2,600 km (1,600 mi) from north to south. The species is native to all regions of the United States east of the 95th meridian west, with only three exceptions, namely the Prairie Peninsula of the Midwest, the coastal prairie in southern Louisiana and southeastern Texas and the swamp prairie of the Florida Everglades. In several other locations, the tree is absent from large areas but still present in a few specific habitats. An example is the Bluegrass region of Kentucky, where it is not found in the dominant open plains, but is present along streams. Here the red maple is not present in the bottom land forests of the Grain Belt, despite the fact it is common in similar habitats and species associations both to the north and south of this area.
The tree’s range ends where the −40 °C (−40 °F) mean minimum isotherm begins, namely in southeastern Canada. On the other hand, the western range is limited by the much drier climate of the Great Plains. Nonetheless, it has the widest tolerance to climatic conditions of all the North American species of maple. The absence of red maple in the Prairie Peninsula is due to the species’ intolerance of fire.
- rubrum does very well in a wide range of soil types, with varying textures, moisture, pH, and elevation, probably more so than any other forest tree in North America. It grows on glaciated as well as nonglaciated soils derived from the following rocks: granite, gneiss, schist, sandstone, shale, slate, conglomerate, quartzite, and limestone. Chlorosis can occur on very alkaline soils, though otherwise its pH tolerance is quite high. As concerns levels of moisture, the red maple grows everywhere from dry ridges and southwest facing slopes to peat bogs and swamps. It occurs commonly in rather extreme moisture conditions, both very wet and quite dry. While many types of tree prefer a south or north facing aspect, the red maple does not appear to have a preference. Its ideal conditions are in moderately well-drained, moist sites at low or intermediate elevations. However, it is nonetheless common in mountainous areas on relatively dry ridges, as well as on both the south and west sides of upper slopes. Furthermore, it is common in swampy areas, along the banks of slow moving streams, as well as on poorly drained flats and depressions. In northern Michigan and New England, the tree is found on the tops of ridges, sandy or rocky upland and otherwise dry soils, as well as in nearly pure stands on moist soils and the edges of swamps. In the far south of its range, it is almost exclusively associated with swamps.
Red Maple is far more abundant today than when Europeans first arrived in North America, where along with its cousin Silver Maple, it may have comprised a mere 5% of forest area and was confined mostly to riparian zones. The density of the tree in many of these areas has increased 6 to 7 fold and this trend seems to be continuing, much of it due to human factors, especially suppression of wildfires which would kill shallow-rooted pioneer species like red maple, but leave mainline forest trees like oaks and hickories untouched. In addition, conservation efforts have caused a major increase in the population of white-tailed deer since the mid-20th century. Deer will readily consume acorns, but leave maple seeds untouched, thus reducing the ability of oaks to regenerate. Concern has been expressed, as the ongoing spread of the red maple is changing the nature of eastern forests by reducing the number of oaks, hickorys and pines that would otherwise dominate. Extensive use of red maple in landscaping has also contributed to the surge in the species’ numbers as volunteer seedlings proliferate. Finally, disease epidemics have greatly reduced the population of elms and chestnuts in the forests of the US. While mainline forest trees continue to dominate mesic sites with rich soil, more marginal areas are increasingly being dominated by red maple.
In the lumber industry Acer rubrum is considered a soft maple. The wood is close grained and as such it is similar to that of A. saccharum, but its texture is softer, less dense, and has a poorer figure and machining qualities. High grades of wood from the red maple can nonetheless be substituted for hard maple, particularly when it comes to making furniture. As a soft maple, the wood tends to shrink more during the drying process than with the hard maples.
Red maple is also used for the production of maple syrup, though the hard maples Acer saccharum (sugar maple) and Acer nigrum (black maple) are more commonly utilized. One study compared the sap and syrup from the sugar maple with those of the red maple, as well as those of the Acer saccharinum (silver maple), Acer negundo (boxelder), and Acer platanoides (Norway maple), and all were found to be equal in sweetness, flavor, and quality. However, the buds of red maple and other soft maples emerge much earlier in the spring than the sugar maple, and after sprouting chemical makeup of the sap changes, imparting an undesirable flavor to the syrup. This being the case, red maple can only be tapped for syrup before the buds emerge, making the season very short.
Red maple is a medium quality firewood, possessing high heat energy, nominally 5.4 MJ/m³ (18.7 million BTU (mbtu) per cord), than other hardwoods such as Ash: 7 MJ/m³ (24 mbtu/cord), Oak: 7 MJ/m³ (24 mbtu/cord), or Birch: 5.8 MJ/m³ (20 mbtu/cord).
Red Maple make vibrant and colorful Bonsai, and have year around attractive features for display.
(Source: Wikipedia, the free encyclopedia)