Acer rubrum (Red Maple) is a tree in the genus Acer, belonging to the family Aceraceae. It is native to the eastern and central parts of North America. The tree is also known under several common names, including soft maple, water maple, scarlet maple and swamp. This attractive ornamental tree is prized for its attractive brightly-colored foliage, which in autumn turns to pink-red, orange and yellow hues.
The Acer rubrum (Red Maple) tree also provides wildlife value. Its fruits are eaten by rodents, while the shoots and leaves are consumed by rabbits and deer. The dry leaves, however, are toxic to horses.
Etymologically, the genus name Acer is of Latin origin. While its direct root is uncertain, it is likely related to the Greek word ‘akastos’, meaning ‘maple’. The epithet rubrum means red, and comes from the red leaves, stem, twigs and fruit of the tree.
Since 1964, the Red Maple has been a state tree of Rhode Island. Interestingly, the largest Red Maple tree in Rhode Island is approximately 43 meters tall, and grows in Great Smokey Mountains National Park.
In its natural habitat, the Acer rubrum tree typically grows 12 to 21 meters tall. Its oval or round crown can be 9 to 15 meters wide. In spite of its rapid growth and potential to grow tall, Acer rubrum makes an excellent bonsai tree. For best results, it is recommended to start growing a Red Maple bonsai tree from a seed. The work on the sapling should begin once it is two years old, or at least 20 cm tall.
This guide provides the foundations of Acer rubrum (Red Maple) bonsai tree care guide.
How Long Does It Take To Grow Acer rubrum (Red Maple) Bonsai?
Acer rubrum (Red Maple) is considered a medium-speed grower. In a natural habitat, the tree typically grows at a rate of 30 and 45 cm per year. Grown outdoors, the tree can fully develop within 25 years. The tree that may live from 100 to 150 years.
With skilled pruning, wiring and repotting, the growth of the Acer rubrum (Red Maple) bonsai tree can be controlled and redirected towards thickening of the twigs and foliage.
How to Plant and Grow Acer rubrum (Red Maple) Bonsai?
It has been said that Acer rubrum (Red Maple) is a strong and forgiving tree, which cannot tolerate only one mistake — underwatering. As a low-maintenance and durable bonsai tree, Acer rubrum (Red Maple) is a wonderful choice for a bonsai beginner.
The easiest way to grow Acer rubrum (Red Maple) bonsai tree is from seeds. It has been reported that typically 25 to 60 percent of the seeds germinate. Seeds can be collected from mature plants which grow outdoors, since the bonsai specimens do not produce seeds.
The seeds should then be planted in a tray filled with horticulture sand, approximately 0.5 to 2.5 cm deep. The tray should then be sealed in a plastic bag and placed in in a fridge for two to three months. Once this period is over, the tray should be placed in warm area, moderately exposed to sunlight. Once every day the plastic bag should be removed, to expose the tray to fresh air. The moisture level should be maintained by spraying water over the sand. When the sprouts finally appear, the plastic back should be completely removed, and the tray should be placed in a sunny and warm area. The first transplantation is recommended to be done once the roots become 2 to 3 cm long.
Another popular method of Acer rubrum (Red Maple) propagation is from cuttings. This involves taking a shoot from a Red Maple stump. Relative to seed propagation, this is a more complex method, since cuttings are difficult to root.
Finally, air layering is one more propagation method common for this tree species. This process takes place when a lower branch of the tree touches the ground and takes root. The newly rooted stem can then be cut away from the parent tree and planted separately from the parent tree.
Position, Lighting and Temperature Requirements
Acer rubrum (Red Maple) bonsai trees require exposure to full sun or moderate shade. Ideally, the tree should get six hours of direct sunlight every day. The tree is adaptable to booth dry and moist conditions, and can also tolerate cooler weather.
Soil and Watering Needs
Acer rubrum (Red Maple) bonsai thrives best on wet to moist, water-retaining soils. It can grow on a variety of soil mediums, including clay, loamy, sandy and acidic soils.
When the temperature is high, the tree requires plenty of water. Another approach is to place the tree pot in a water tray. A useful rule of thumb is that, in the case of Acer rubrum, overwatering is better than underwatering. When the temperature is very high, if the tree receives insufficient amount of water, it can deteriorate or even die from drying within a single day.
For best results, it is recommended to use slightly acidic, standard bonsai soil or organic compost mix. Highly acidic soils should be avoided, as the high level of manganese contained in them can cause chlorosis (paling or yellowing of the leaves due to a lack of chlorophyll).
Acer rubrum (Red Maple) bonsai requires regular application of fertilizer. During spring, fertilizer should be applied every week during spring and summer, and twice a month during fall and winter. The fertilizer should not contain excessive amounts of nitrogen. Some sources recommend a combination of worm castings, bone and blood meal, cottonseed meal and other organic components.
How to Care for Your Acer rubrum (Red Maple) Bonsai?
While working with the Acer rubrum (Red Maple) bonsai tree, bonsai beginners can apply the standard rules and procedures. It is important, however, to keep two things in mind. The first is to keep the root system shallow. The second is to control the quick thickening of the top branches. The roots can be controlled by avoiding deep containers. To control top dominance, strong top growth needs to be cut back to one node.
Pruning and Wiring
There are several styles in which the Acer rubrum (Red Maple) bonsai tree can be developed, including clump, group, informal upright, slanting, and forest. A balanced combination of pruning and defoliation, regularly performed, can result in smaller leaves and delicately shaped twigs.
Wiring should be performed with utmost care, since the bark of this tree is very sensitive and can easily scar. Wiring can be used at any stage of the bonsai tree development and, when skillfully performed, can produce refined tree shapes. Rubber-coated aluminum wire might be the best and safest choice for the tree. However, experienced bonsai enthusiasts recommend limited use of wiring. They recommend pruning as a more appropriate method for shaping an Acer rubrum (Red Maple) bonsai tree.
Pruning primarily boosts ramification. It also controls the distribution of twigs and open spaces. To shorten the distance between the leaves and new nodes, it is recommended to perform frequent pinching of new nodes. However, once a branch is removed, a scar forms, and inducing new growth at that place becomes quite challenging.
Defoliation (removal of all the leaves in order to make leaves smaller and stimulate denser foliage) can be performed, as long as the leaf stems are not removed. Pulling off the leaf stems can damage the buds at the base of the stalks. When the leaves are properly cut off, within two to three weeks those buds of small, brightly-colored leaves will sprout.
Compared to other deciduous trees, Acer rubrum (Red Maple) bonsai tree needs more root mass. To meet this requirement, the tree should be planted in a larger and deeper pot. Repotting should be performed in spring, before the leaf buds begin to open. Saplings and smaller trees can be bare rooted. Larger and well-developed ones need to be first balled and burlapped. Root pruning should be performed annually on younger specimens, and once in two to three years on mature bonsai trees. The roots should be pruned systematically, so that they remain lateral and coplanar.
Pests and Diseases
The Acer rubrum (Red Maple) bonsai tree is vulnerable to several insects, including the leaf stalk borer, petiole-borer, gall mites, aphids and scales (especially the cottony maple scale). These pests can damage the tree in different ways. Insect infestations can cause unsightly changes on the surface of the leaves, such as galls and fuzzy patches. In severe cases, this can lead to total leaf drop. Preventive measures include timely use of pesticides.
During the rainy seasons, the Red Maple bonsai tree is also prone to anthracnose, a disease which causes appearance of light brown patches on the leaves. To prevent the occurrence of this disease, in spring the plant needs to be sprayed with fungicides.
Another common problem is the growth of girdling roots, which wrap around the base of the trunk, affecting the flow of nutrients and water. Early detection is crucial. Once identified, the girdling roots should be removed.
Insufficient watering can case scorch during seasons of high temperatures and intensive winds. To prevent it, regular watering is necessary.