Amur Cork

Basic Information
Tree ID: 
Genus and species: 
The Amur Cork Tree, named for its corky inner bark, is an interesting specimen. The Ainu people in Japan used parts of this tree, which they call shikerebe-ni, as a painkiller. It is also a widely-used source of huàng bà, an important herb used in traditional Chinese medicine. However, in the United States, it crowds out native species, diminishes other trees’ access to light with its shelf-like branching, produces many seeds, and does not have many seed predators. Consequently, this tree is able to successfully outcompete native trees (e.g. oaks, hickories) and shrubs; it also suppresses the growth of canopy trees. Consequently, it has become invasive in parts of New York, Pennsylvania, Illinois, and Virginia. In fact, in Massachusetts, it is considered a "noxious weed."
Al Nurani & Sukriti Mohan
Collected Data
Tree shape: 
medium-sized (30-40ft tall), thick trunk, wide crown
Date of tree entry: 
17.20 m
Diameter at breast height: 
0.60 m

The Amur Cork actually gets its name from the bark's thick appearance and corky/spongey texture. In young trees, the Amur Cork's bark has a light golden brown color, while more mature trees have barks that appear gray/brown. The inner bark, pictured, is neon yellow just below the surface.
Twigs & branches
As the Amur Cork grows, the branches spread very widely, creating a canopy-like overhead. There are several thick main branches that shoot off the tree's trunk, and these branches can be quite picturesque, moving in all different directions. These large branches give way, in turn, to smaller and thinner branches. When the tree reaches maturity, the branches start to droop slightly, creating a flat-surfaced top. The tree's twigs are brown and smooth, and contain scattered white lenticels -- pores that facilitate gas exchange between the atmosphere and internal tissue of the tree.
The leaves on the Amur Cork are broad, elliptic, flat, and pinnately compound, meaning that a row of leaflets form on either side of the rachis, the leaf's main stem. All of the leaflets are similar in shape and size, and grow opposite each other. The entire leaf is normally 10-15 inches long, composed of 5-13 leaflets that are each 2-5 inches long and 1-2 inches wide. In the spring and summer, the leaflets are dark green and glabrous (smooth) on the upper surface, but pale green and sparsely hairy along the rachis on the lower surface. The petioles and rachises are light green, pale reddish green, or sometimes nearly white. In autumn, however, the leaves transform into a beautiful bronze or bright yellow color before falling off as winter approaches. Although the leaves are beautiful to look at, be careful about crushing them! Upon being crushed, the leaves are known to give off a distinct citrus-like smell that has been likened to the smell of a skunk.
Reproductive Structures
The flowers of the dioecious Amur Cork appear in small clusters between two to four inches. All of the flowers are staminate (male) or pistillate (female), and they occur on separate trees. Flowers are approximately 1/8 inches wide. The calyx is green or maroon and has five teeth. The corolla is yellow or maroon and has five lobes. Female flowers have one carpel each, and male flowers each have five stamens with large yellow anthers. Flowers bloom between the late spring and early summer for about two weeks.
Female trees produce clusters of drupe fruits with diameters between 0.25-0.5 inches from mid-June to mid-July. They are initially a green color but turn black in the autumn. They remain on the tree until the early winter. Male trees don’t produce fruit. The Amur Cork produces many seeds, which are usually dispersed by birds and water in streams nearby. Native birds (e.g. the Northern robin) eat the drupe fruits during the fall and winter. Usually, seeds are dispersed within a few hundred yards of the parent tree’s location. They remain viable for years, making this tree even more capable of outperforming other trees in the area.
  • Fall
  • Winter
  • Spring/Summer
Natural range of distribution: 
The Amur Cork is native to northern China, Korea, and Japan. The tree was brought to the United States around 1856. The tree has mostly been planted in parks and urban settings, but is considered an invasive species in certain parts of northeastern America due to its ability to shade out other plants after dominating an area. The Amur Cork grows well in full sun, but is also quite tolerant of shady areas, especially in its early years. Similarly, although they grow well in moist soil, they are tolerant of dry soil for certain periods of time. They are able to grow in a wide soil pH range (5.0-8.2). These attributes contribute to the tree's ability to outgrow other plants.
Origin, history, and uses: 
The tree’s bark has been used for generations in Chinese, Indian, and Japanese traditional medicine. In China, it has been used for the treatment of meningitis, pneumonia, and tuberculosis. In addition, the bark of the tree has compounds that may protect cartilage against arthritis, act as a chemopreventive agent for those with lung cancer, and prevent the growth of prostate tumors. The oil of the fruits, which interestingly can also serve as an insecticide, is also used in medicine, specifically to treat pancreatitis and reduce cholesterol and blood sugar levels.
In addition, the yellow bark on the inside was once used to make dyes and yellow paper in ancient China. This tree was introduced to the United States in 1856, and by 1933, it had been naturalized in the forests of the New York Botanical Garden. Today the tree is mostly used as an ornamental and landscape tree, especially on college campuses like Yale.
The flowers of the Amur Cork tree appear in late May to early June. Pollination occurs during the summer. The leaves, which are dark green in the summer, transition into a golden color in the fall. They grow very quickly, and they also drop quickly in the fall. The fruits mature to a black color in September, moving into winter. In the late fall and winter, birds and other animals eat them and disperse the seeds. The Amur Cord is a resilient tree that can withstand a number of climates (specimens have even been found in Antarctica!), and this has contributed to it becoming invasive in the United States. As the tree is young, its outer bark is reddish brown, and its inner bark is bright yellow. As the tree ages, the bark of the tree becomes ridged and corky and the branches begin to droop.


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