The deciduous tree of amur maple has fragrant white flowers that change into a brilliant orange-red color in autumn. It grows fast but lives long, and the flowers don’t show until the tree matures. It grows at the edges of bogs and open forests and requires just a moderate amount of maintenance.
I. Appearance and Characteristics
Acer ginnala, the Amur maple, is a plant species with woody stems native to northeastern Asia from easternmost Mongolia east to Korea and Japan, and north to the Russian Far East in the Amur River valley.
Acer ginnala is a deciduous spreading shrub or small tree growing to 3–10 m (9.8–32.8 ft) tall, with a short trunk up to 20–40 cm (8–16 in) diameter and slender branches. The bark is thin, dull grey-brown, and smooth at first but becoming shallowly fissured on old plants. The leaves are opposite and simple, 4–10 cm (1+1⁄2–4 in) long and 3–6 cm (1+1⁄4–2+1⁄4 in) wide, deeply palmately lobed with three or five lobes, of which two small basal lobes (sometimes absent) and three larger apical lobes; the lobes are coarsely and irregularly toothed, and the upper leaf surface glossy.
The leaves turn brilliant orange to red in autumn, and are on slender, often pink-tinged, petioles 3–5 cm (1+1⁄4–2 in) long. The flowers are yellow-green, 5–8 mm (0.20–0.31 in) diameter, produced in spreading panicles in spring as the leaves open. The fruit is a paired reddish samara, 8–10 mm (0.31–0.39 in) long with a 1.5–2 cm (5⁄8–3⁄4 in) wing, maturing in late summer to early autumn.
Acer ginnala is grown as an ornamental plant in northern regions of Europe and North America. It is the most cold-tolerant maple, hardy to zone 2. It is naturalised in parts of North America. Planted on exceptional sites facing south west with consistent moisture and light loamy soils, this tree can grow 1 m (3 ft 3 in) per year making it a fast grower. It is often planted as a shrub along borders.
In the UK it has gained the Royal Horticultural Society’s Award of Garden Merit.
It is also valued in Japan and elsewhere as a species suitable for bonsai.
It is a nonnative invasive species in parts of northern North America.
II. How to Grow and Care
Amur maple is a hardy deciduous shrub with minimal care requirements, making it suitable for gardeners of all levels. It thrives in well-drained soil and full to partial sun exposure. Special care points include its adaptability to various soil types and its moderate tolerance to drought once established. Pruning is necessary to maintain the desired shape and size, as amur maple can become invasive if not managed appropriately.
Sunlight
Amur maple thrives best in conditions of full sun, which denotes an unfiltered exposure to sunlight for at least 6-8 hours each day. This optimum light intensity promotes vigorous growth and fosters a robust health constitution in the plant. Although amur maple exhibits a tolerance for partial sun, where the plant receives some direct sunlight interspersed with shade, sustained deviations from full sun can result in subdued growth vigor. Under less than ideal light, amur maple may exhibit adaptive traits, such as leaf adjustments, to optimize light absorption. Ideally suited for outdoor growth, amur maple should be sited in locations where direct sunlight is plentiful to ensure its healthy development.
Temperature
The amur maple has good cold resistance and is able to tolerate low temperatures. The amur maple is native to the margins of forests in China, Japan, and North Korea, so these trees generally prefer a humid environment. Most amur 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 regions with moderate moisture, amur maple has adapted to a balanced water regime. It thrives when the soil is allowed to dry slightly between watering sessions, reflecting its resilience and preference for moderate humidity rather than saturation. Accordingly, it benefits from watering once every 1-2 weeks. As an outdoor plant often subject to varying weather conditions, amur maple exhibits remarkable adaptability but performs best when rainfall patterns align with its growth cycles, ensuring consistent hydration without over-saturation.
Soil
The amur 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
For optimal health, amur maple thrives with balanced nutrition fertilizers, such as 10-10-10, applied annually in early spring to encourage vigorous growth. Additionally, high nitrogen fertilizers can be used to support dense foliage development. It’s beneficial to apply 1-2 inches away from the trunk, extending to the drip line at the recommended label rate. Over-fertilization must be avoided to prevent root burn and excess growth. During amur maple’s dormant period in winter, fertilization should cease. In the growth phases, particularly for young amur maple, more frequent feeding will establish robust root systems. Always water thoroughly post-fertilization to aid nutrient absorption.
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 an amur 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 an amur 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
The versatile and hardy amur maple is well-suited for propagation through the method of cutting. Enthusiasts should select healthy, semi-hardwood stem cuttings and prepare them by making a clean cut below a leaf node. For optimal root development, treat the cut end with rooting hormone and plant in a well-draining, sterile growing medium under high humidity conditions. Careful monitoring for water and indirect light will ensure successful propagation. Maintain a stable environment to foster growth until the cuttings are robust enough for transplantation.
Transplanting
The best time to relocate amur maple is during the warmer embrace of late spring to early summer, ensuring a gentle transition. Select a sun-kissed spot with well-draining soil to encourage robust growth post-transplant.
III. Uses and Benefits
Amur maple is one of the most resilient and decorative smaller maples you can grow in a garden, as a specimen tree, an understory tree, in a container, and even in the form of bonsai. The crown is broad, rounded to open, and the small, three-lobed leaves turn various hues of red and orange in the fall. The trunk can take on irregular shapes when growing, making certain specimens additionally attractive.
