Rough-barked maple starts out as a bush but almost always ends up as a tall tree. Its reddish trunk is very scaly and complements the bluish-green undersides of its leaves. It makes a great standalone tree for a garden or a park after 15 years of slow to moderate growth.
I. Appearance and Characteristics
Acer triflorum, the three-flowered maple, is a species of maple native to hills of northeastern China (Heilongjiang, Jilin, Liaoning) and Korea.
It is a deciduous tree that reaches a height of about 25 meters (82 ft) but is usually smaller. It is a trifoliate maple related to such other species as Manchurian Maple (Acer mandshuricum) and Paperbark Maple (Acer griseum). It has yellowish-brown exfoliating bark that peels in woody scales rather than papery pieces like Acer griseum.
The leaves have a 2.5–6 centimeters (0.98–2.36 in) petiole and three leaflets; the leaflets are 4–9 centimeters (1.6–3.5 in) long and 2–3.5 centimeters (0.79–1.38 in) broad, with serrated margins, the central leaflet the same size as or slightly larger than the two side leaflets. The flowers are yellow, produced in small combs of three small flowers each, hence the name. The samaras are 3.5–4.5 centimeters (1.4–1.8 in) long and 1.3–2 cm broad, hairy, the nutlet with a woody shell.
Even more than its relatives, three-flower maple has a spectacular fall color that may include brilliant orange, scarlet, purple and gold. It is one of the few trees to develop good fall color in shade.
The species was first introduced to cultivation in 1923. Although common in maple collections, it is rarely seen in cultivation outside of arboreta.
It grows at a slow to moderate rate and prefers moist, well drained soil; growth is often shrub-like in cultivation. It is relatively tolerant of drought and clay compared to its close relatives. It does not tolerate wet or over-compacted soil. Propagation is similar to that required for Acer griseum and the number of viable seeds is likewise very small.
In Great Britain, the largest specimens are up to 13 m (43 ft) tall, and 60 cm (24 in) trunk diameter (Tree Register of the British Isles). It has gained the Royal Horticultural Society’s Award of Garden Merit. In the United States, mature specimens can be seen at Arnold Arboretum in Boston, Massachusetts.
II. How to Grow and Care
Rough-barked maple is considered to have an easy care level, well-suited for many temperate gardens. Key care needs include planting in well-drained soil and providing adequate water, especially during dry periods. Special care points involve protecting rough-barked maple from strong winds and perhaps giving some shelter in winter to younger trees, as they can be susceptible to cold damage. Prune selectively to maintain its attractive, three-flowered branching structure.
Sunlight
The rough-barked maple has a certain requirement for sunlight and prefers a partially shaded area. In cases of exposure to direct sunlight in the summer, the leaves of most varieties will wither, so shading is required. As the plants get older and their root system grows, this condition will be less of a problem. A few varieties will tolerate exposure to direct sunlight, such as ‘Beni Maiko’ and ‘De Shojo’. Some weeping varieties can also tolerate exposure to direct sunlight, such as ‘Ao Shidare’.
Sunlight conditions will directly affect the ornamental appearance of rough-barked maple leaves. In the spring, sufficient sunlight will make the maple leaves more vivid, while in cases of insufficient sunlight or partial shading the leaf color may fade. During the fall, sunlight can also affect the leaf color. For potted plants, full exposure to sunlight is recommended during the spring and the fall, with partial shading in the summer.
Temperature
The rough-barked maple has good cold resistance and is able to tolerate low temperatures. The rough-barked maple is native to the margins of forests in China, Japan, and North Korea, so these trees generally prefer a humid environment. Most rough-barked maple plants have shallow root systems, so they should be watered frequently during the summer. For some varieties, a sprayed mist should be provided during the summer to increase the humidity of the air around them.
Watering
Originating from temperate regions, rough-barked maple has adapted to withstand periods of low water availability, exhibiting moderate drought tolerance. Ideally, it thrives with watering once every 1-2 weeks, allowing the soil to dry slightly between sessions. As a deciduous tree commonly grown outdoors, rough-barked maple’s water needs fluctuate with the seasons; during its active growth in spring and summer, consistent moisture aids in its lush foliage development.
Soil
The rough-barked 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 rough-barked 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 rough-barked 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 rough-barked 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
An ornamental deciduous tree prized for its peeling bark and trifoliate leaves, rough-barked maple thrives when propagated by cuttings, a method suitable for ensuring genetic consistency with the parent plant. Cuttings should be taken from healthy, disease-free branches, ideally with several nodes. These should then be planted in well-drained, fertile soil, maintaining adequate moisture levels without overwatering. Rooting hormone may enhance success rates. Establishing a new rough-barked maple requires patience, as the young plant should be carefully monitored for growth and pests.
Transplanting
The prime time to transplant rough-barked maple spans from the awakening of early spring to the gentle closure of late spring, or as autumn hues deepen. For success, choose a location blessed with moist, well-drained soil. Gentle guidance in site selection enhances rough-barked maple’s transplanting triumph.
III. Uses and Benefits
Rough-barked maple is perfect as a specimen plant in cottage gardens, city gardens, or foundation plantings.
