The red maple is a common North American tree with distinctive red leaves and flower buds. Its sap can be made into maple syrup and the wood is good for furniture. Though non-toxic to humans, the leaves are very toxic to horses. According to the U.S. Forest Service, red maple is the most common tree in eastern North America.
| Common name | Carolina Maple, Red Maple, Scarlet Maple, Soft Maple, Swamp Maple |
| Botanical name | Acer rubrum |
| Family | Sapindaceae |
| Species | rubrum |
| Origin | Newfoundland to Florida West to Minnesota Oklahoma and Texas. |
| Life cycle | Woody |
| Plant type | Native Plant |
| Hardiness zone | 2, 3, 4, 5, 6, 7, 8, 9 |
| Sunlight | Full Sun |
| Maintenance | Low |
| Soil condition | Clay |
| Soil ph | Acid |
| Drainage | Well-Drained |
| Growth rate | Fast |
| Spacing | more than 60 ft. |
| Harvest time | Spring |
| Flowering period | Spring |
| Height | 4- 120 ft. |
| Width | 4- 120 ft. |
| Flower color | Burgundy, Red |
| Leaf color | Gold, Yellow |
| Fruit color | Brown, Copper |
| Stem color | Gray, Silver |
| Fruit type | Samara |
| Fruit benefit | Showy |
| Leaf benefit | Showy |
| Flower benefit | Fragrant |
| Garden style | Butterfly Garden |
| Uses | Recreational Play Area |
I. Appearance and Characteristics
Acer rubrum, the red maple, also known as swamp maple, water maple, or soft maple, is one of the most common and widespread deciduous trees of eastern and central North America. The U.S. Forest Service recognizes it as the most abundant native tree in eastern North 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.
Though A. rubrum is sometimes easy to identify, it is highly changeable in morphological characteristics. It is a medium to large sized tree, reaching heights of 27 to 38 m (90 to 120 ft) and exceptionally over 41 m (135 ft) in the southern Appalachians where conditions favor its growth.
The leaves are usually 9 to 11 cm (3+1⁄2 to 4+1⁄4 in) long on a full-grown tree. The trunk diameter often ranges from 46 to 88 cm (18 to 35 in); depending on the growing conditions, however, open-grown trees can attain diameters of up to 153 cm (60 in). The trunk remains free of branches until some distance up the tree on forest grown trees, while individuals grown in the open are shorter and thicker with a more rounded crown. Trees on poorer sites often become malformed and scraggly. Generally the crown is irregularly ovoid with ascending whip-like curved shoots.
The bark is a pale gray 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 ft 3 in).
The leaves of the red maple offer the easiest way to distinguish it from its relatives. As with all North American maple trees, they are deciduous and arranged oppositely on the twig. They are typically 5–10 cm (2–4 in) long and wide with three to five palmate lobes with a serrated margin. The sinuses are typically narrow, but the leaves can exhibit considerable variation. When five 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 five lobes. The upper side of A. rubrums 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 (4 in) long. The leaves can turn a characteristic brilliant red in autumn, but can also become yellow or orange on some individuals. Soil acidity can influence the color of the foliage and trees with female flowers are more likely to produce orange coloration while male trees produce red. The fall colors of red maple are most spectacular in the northern part of its range where climates are cooler.
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, collateral buds may be present, as well. The buds form in fall and winter and are often visible from a distance due to their large size and reddish tint. The leaf scars on the twig are V-shaped and contain three 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 late winter to early spring, from December to May depending on elevation and latitude, usually before the leaves. The tree itself is considered polygamodioecious, meaning some individuals are male, some female, and some monoecious.
Under the proper conditions, the tree can sometimes switch from male to female, male to hermaphroditic, and hermaphroditic to female. The red maple will begin blooming when it is about 8 years old, but it significantly varies from 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, usually at the twig tips. The staminate flowers are sessile.
The pistillate flowers are borne on pedicels that grow out while the flowers are blooming, so that eventually the flowers are in a hanging cluster with stems 1 to 5 cm (1⁄2 to 2 in) long. The petals 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 schizocarp of 2 samaras, each one 15 to 25 mm (5⁄8 to 1 in) long. Prior to dehiscence, the wings of the fruit are somewhat divergent at an angle of 50 to 60°. They are borne on long slender pedicels 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.
II. How to Grow and Care
Sunlight
These trees can thrive under the direct sun but are also tolerant of partial shade.
Watering
The red maple prefers the soil to be kept moist, especially during the summer, because dry weather can cause its leaves to scorch and even fall off in severe cases. During the summer, in addition to watering the roots, foliage can be sprayed during the evening to increase the humidity.
- In the summer, seedlings growing in pots may need watering twice a day, in the morning and the evening.
- In the spring and fall, watering should be carried out depending on the actual conditions. Watering can be reduced slightly as the temperature drops in the fall, which will help the leaves to change color.
- In the winter, it is only necessary to ensure that the soil does not dry out.
Attention should be paid to the watering of seedlings grown in gardens during the early stages. At later stages, water should be supplied according to the weather, that is if there is no rain for more than two weeks in the summer.
Soil
The red maple does not have many specific requirements for soil. It is a forest native, so it prefers well-drained soil that is rich in humus and slightly acidic. Its main root will extend deep into the soil, but its tiny fibrous roots will be concentrated near the soil surface, so accumulated water in the soil tends to cause root rot.
Fertilizing
Potted seedlings should be given slow-release fertilizer only. For seedlings grown in gardens, fertilizer should be applied three times a year: once in the early spring, once in early summer for the growth period, and once in the fall.
Planting Instructions
The best time for planting or transplanting a red maple is following defoliation in the fall. At this time, the leaves will have fallen off so there is little transpiration and water loss can be avoided. In addition, the root system will still be growing at this time, preparing for regrowth the following spring. Transplanting should be avoided on the coldest days because cold wind can kill some of the shoots and branches. During the winter, in areas that cannot be sheltered from the wind, it is recommended to cover the branches.
Pruning
Pruning is mainly used to enhance internal ventilation, improve shoot formation, promote growth, and for shaping. The common approach to pruning is to remove any old or weak branches, remove any branches that disrupt the shape of the tree, and remove any branches that cross other branches. Pruning is used to control the plant according to the required height and shape. Generally, this follows the “Y-type” pruning method.
It is possible to prune a red maple throughout the year, but the coldest winter months should be avoided to prevent damage to the plant. Major pruning to shape a maple can be performed following defoliation in the fall, or prior to leaf growth in the spring. It is recommended to prune in the fall because withered and full buds can be easily distinguished.
According to the shaping plan, you can prune any withered buds and keep the full ones, thus making your tree healthier. For pruning in the summer, diseased, weak, or dead branches can be removed, mainly to enhance the tree’s ventilation.
If grown as a potted plant, the roots can easily occupy the entire flowerpot due to the limited space. This can make a red maple prone to aging if an old flowerpot is not changed. It is recommended that old roots are pruned during the dormancy period, that is, cut off any old, coarse, diseased, and weak roots.
Propagation
These trees are easily propagated from seeds or by cuttings. These trees produce plenty of seeds that should be collected when they start dropping from the tree. Cuttings from mature trees are difficult to root but are still a viable method to propagate the tree.
- Seed Propagation
Prepare a few pots with good drainage and fill them with soil. The pots should be big enough to give the seedling space to grow before it can be transplanted. Collect the seeds when they are fully mature.
Plant each seed in the individual pots, burying them 1-2 inches into the soil. Move them to a sunlit location, and water regularly without over-saturating the soil. Seeds will typically begin germinating after 10 days.
- Cutting Propagation
Prepare a few pots that drain well and fill with soil amended with perlite and peat. Select a healthy growing shoot after the tree has finished seeding and take a cutting between 6-8 inches long.
Remove the leaves from the lower half of the cutting. Make an inch-long shallow incision on both sides of the cutting’s base and coat the incisions with rooting hormone.
Bury the end in the prepared pot and water lightly. Place the cutting in a sunlit location and water regularly without drenching the soil. Prevent the remaining leaves from drying by misting them regularly.
Pests and Diseases
Aphids, scale, and borers are a few pests that might plague these trees.
The bulk of the diseases that affect this tree are mostly cosmetic, generally affecting the leaves, although some infections can attack internally and kill the tree through the roots.
Verticillium wilt infects the circulatory system through the roots and prevents nutrients and water from getting to the leaves and branches. Infected dead leaves will drop to the soil, potentially spreading to other trees.
Symptoms include yellow, wilting leaves, leaf loss, stunted leaves, and discolored wood under the bark. There is no cure, although with proper care the tree can recover. This typically happens in summer. Mildly infected trees usually slowly decline, while more severely infected trees must be destroyed and the soil should be fumigated.
Root rot is common in wet and poor drainage conditions. This attacks healthy tissues and comprises the circulatory system, preventing nutrients and water from reaching the leaves and branches. This is commonly caused by fungal infections from wet soil and is fatal for the tree.
While tar spot isn’t life-threatening, this fungal infection affects the leaves, causing yellow and black spots and leading to leaf drops. There is no treatment for this other than prevention by collecting and disposing of infected leaves that fall off.
Anthracnose disease affects both leaves and branches and usually happens under wet weather conditions. Lower leaves and branches are more prone to infection. Symptoms include shriveled leaves, curled leaves, brown spots on leaves, and leaf veins becoming discolored. There is no cure – prune dead branches and remove fallen leaves.
Powdery mildew doesn’t harm the tree, as the powder simply sits on the leaves and can be removed using horticultural oil or brushed off. The roots will not be affected and the fungus doesn’t damage the leaves.
Leaf scorch usually occurs in summer, under hot and dry conditions, when the tree cannot provide sufficient water to the leaves. Increase watering, add mulch to sustain moisture and prune dead branches.
III. Uses and Benefits
- Ornamental uses
Due to its attractive fall foliage and pleasing form, it is often used as a shade tree for landscapes.
- Culinary uses
Red maple is 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.
- Medicinal uses
Native Americans used red maple bark as a wash for inflamed eyes and cataracts, and as a remedy for hives and muscular aches. They also would brew tea from the inner bark to treat coughs and diarrhea. Pioneers made cinnamon-brown and black dyes from a bark extract, and iron sulphate could be added to the tannin from red maple bark in order to make ink.
- Other uses
In the lumber industry Acer rubrum is considered a “soft maple”, a designation it shares, commercially, with silver maple (A. saccharinum). In this context, the term “soft” is more comparative, than descriptive; i.e., “soft maple”, while softer than its harder cousin, sugar maple (A. saccharum), is still a fairly hard wood, being comparable to black cherry (Prunus serotina) in this regard. Like A. saccharum, the wood of red maple is close-grained, but its texture is softer, less dense, and has not as desirable an appearance, particularly under a clear finish.
However, the wood from Acer rubrum, while being typically less expensive than hard maple, also has greater dimensional stability than that of A. saccharum, and also machines and stains easier. Thus, high grades of wood from the red maple can be substituted for hard maple, particularly when it comes to making stain/paint-grade furniture. Red maple lumber also contains a greater percentage of “curly” (aka “flame”/”fiddleback”) figure, which is prized by musical instrument/custom furniture makers, as well as the veneer industry. As a soft maple, the wood tends to shrink more during the drying process than with the hard maples.
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