This is the first half of a two part series on red maple. The following examines the tree’s developmental traits, distribution and habitat, longevity, height, leaves, twigs, flowers, fruit, and seed production.
Introduction
Red maple (Acer rubrum), also known as swamp maple, water maple, Drummond red maple, Carolina red maple, or soft maple, is one of the most widespread deciduous trees of eastern and central North America. The U.S. Forest Service recognizes it as the most common species of tree in the United States. Many of its features are variable in form. This is especially noticeable on the many red maple cultivars available for selection. Red maple’s flowers, petioles, twigs, and seeds are appealing shades of red. Its most distinguishing characteristic is its brilliant deep scarlet foliage in autumn.
Red maple flourishes in a wide range of site and soil conditions; more so than any other tree in eastern North America. Due to its striking features, and adaptability, it is often used as a shade tree for landscapes. Red maple can be considered weedy or invasive. In forests across much of the eastern United States, red maple has been displacing deciduous trees like oaks, as well as pines and hickories.
Developmental Traits
Red maple is typically easy to identify. However, due to its wide range, there is significant variation in the tree’s morphological characteristics. Individuals in the north flush the earliest, and have the most vibrant fall color. They also set their buds earlier, which increases their resistance to winter injury. Individuals in the south develop almost exclusively in swamplands. They flush later than their northern counterparts, and have a more modest fall color. Red maples that grow in open areas tend to be shorter and thicker, with a rounded crown. In many cases, the crown is irregularly ovoid with ascending whip-like shoots.
Distribution and Habitat
Red maple is one of the most abundant deciduous trees of eastern and central North America. It has the widest tolerance to climatic conditions of all North American species of maple. In the United States, it ranges most commonly from New England to the Middle Atlantic states. It can also be found in northern Minnesota, northeastern Wisconsin, Illinois, Missouri, eastern Oklahoma, eastern Texas, upper Michigan, and Florida. In Canada, red maple has been reported from southern Newfoundland, Nova Scotia, and southern Quebec to southern Ontario, and southeastern Manitoba.
Throughout its range, red maple has become connected with more than seventy different commercial tree species. Some of its more common associates include red spruce, balsam fir, eastern hornbeam, striped maple, northern white-cedar, aspen, black ash, pin cherry, black cherry, northern red oak, American elm, chestnut oak, Virginia pine, yellow-poplar, silver maple, black gum, swamp white oak, and loblolly pine.
Longevity
Red maple has a short to medium lifespan. It reaches maturity at around 70 to 80 years, and seldom lives longer than 150 years.
Height
Red maple is a medium to large sized tree. Average mature trees reach a height of 60 to 90 feet, with a 40 foot spread; outliers may occasionally reach heights of up to 115 feet. Seedlings are tallest in the north-central and east-central parts of the range.
Leaves
The leaves of red maple are one of the tree’s most distinguishing features. They are typically two to four inches in length and width, with three to five palmate lobes. When five lobes are present, the three at the terminal end are larger than the two near the base. Red maple leaves have serrated margins, and narrow sinuses. Depending on the growing conditions, leaves may exhibit considerable variation. The upper side of the leaf is light green; the underside is white, with either a glaucous, or hairy coating. Leaf stalks are usually red, and can grow up to four inches long. Leaves often turn a brilliant red in autumn, but may also become yellow or orange.
Twigs
Twigs on red maple are varying shades of red. They have small lenticels, and are somewhat shiny. Dwarf shoots are often present on many branches. Buds are usually blunt and greenish to reddish in color. Lateral buds are slightly stalked; collateral buds may be present as well. Buds form in fall and winter, with a reddish tint. Leaf scars on the twig are v-shaped, and contain three bundle scars.
Flowers
Red maple is one of the first plants to flower in spring. Flowers appear in spring from March to May, usually emerging several weeks prior to vegetative budburst. In the southern range, flowers may appear as early as January. Flowering occurs on all branches in the upper portion of the crown. Flowers are generally red, though on some individuals they may be a greenish-yellow. Flowers have five small petals, and are lineal to oblong in shape. They are small, with slender stalks.
Red maple is considered Polygamodioecious. meaning individuals may be entirely male, entirely female, or monoecious. Monoecious trees produce both male and female flowers, which generally appear in separate sessile clusters.
Fruit
On red maple, fruit is a double samara, with somewhat divergent wings. Samaras are borne on long slender stems, varying from brown to red in color. They can grow from one half inch to three quarters of an inch long. Samaras ripen from April to June before leaf development has completed. After ripening, seeds are dispersed for a one to two week period from April to July. Red maple fruits exhibit geographical variation. In the northern range, red maples produce samaras that are shorter but heavier than those found in the southern range. As a result of this variation, red maple is a popular choice for cultivation. It is especially useful for creating urban cultivars with a greater resistance to air pollution, and drought.
Seed Production
Red maple produces a crop of seeds each year, with a bumper crop often occurring every second year. A tree between two and eight inches in diameter can produce between 12,000 and 91,000 seeds in a single growing season; a tree with a one foot diameter can produce nearly one million seeds. Red maple yields one of the smallest seeds of any species of maple.
Seeds are epigeal, meaning germination takes place above the ground. Seeds tend to germinate in early summer, shortly after they have been released. With consistent warm temperatures, red maple can produce seeds with very little light or moisture. If seeds are densely shaded, germination will not occur until the following spring. Most seedlings will not survive in forested settings. However, they provide a rich source of organic material. Fertilization can significantly increase seed yield for up to two years following application.
Additional Resources:
https://www.na.fs.fed.us/pubs/silvics_manual/volume_2/acer/rubrum.htm
http://www.fs.fed.us/database/feis/plants/tree/acerub/all.html
To learn more about red maple, check out the second half of our two part series. It examines the tree’s root development, soil and topography, damaging agents and pests, allergenic potential, and some of its additional uses.
Photograph courtesy of Heng Wang.
