The amur Cork Tree, or Phellodendron amurense, is a tree native to Eastern Asia, which has shown invasive tendencies in North America when it escapes ornamental planting. Because of this invasive nature, only cultivated males are allowed to be planted in many areas. The lumber is highly prized for its ability to resist rotting.
I. Appearance and Characteristics
Phellodendron amurense is a species of tree in the family Rutaceae, commonly called the Amur cork tree. It is a major source of huáng bò (Chinese: 黄柏 or 黄檗), one of the 50 fundamental herbs used in traditional Chinese medicine. The Ainu people used this plant, called shikerebe-ni, as a painkiller. It is known as hwangbyeok in Korean and (キハダ) kihada in Japanese.
It is native to eastern Asia: northern China, northeast China, Korea, Ussuri, Amur, and Japan, the Amur cork tree is considered invasive in many parts of North America. The State of Massachusetts lists it as a noxious weed.
It is noted for its attractive shape, bark and foliage. It is indigenous to moist soils in the valley of the Amur River which serves as the boundary between Siberia and China. It typically grows 30-45’ tall with a short trunk and low horizontal branching. Some mature specimens at the Missouri Botanical Garden have very large lower branches that gracefully dip to touch the ground many feet from the trunk. Grayish-brown bark on mature trees is ridged and corky. Compound, odd-pinnate, yellowish green to green leaves have 5-11 leaflets (each leaflet to 4 1/2” long). Foliage turns an undistinguished yellow in fall. This species is dioecious (separate male and female trees). Non-showy, yellowish green flowers appear in panicles in May-June.
Pollinated flowers on female trees give way to fleshy pea-sized fruits (1/2” diameter drupes) which mature to black in fall (October) and persist well into winter. Foliage and fruits are unpleasantly aromatic when bruised, which is somewhat characteristic of the Rue family to which this stately tree belongs.
Genus name comes from the Greek words phellos meaning cork and dendron meaning a tree for the corky bark.
Specific epithet refers to the Amur River which serves as the boundary between Siberia and China where the species is native.
The name cork tree is in reference to the resemblance of the bark of this tree to the bark of the true cork tree, Quercus suber, which is an unrelated oak family member.
II. How to Grow and Care
Sunlight
Amur Cork Tree thrives in full sun conditions, demanding a significant amount of direct light to foster its growth and enhance its health. While it can adapt to less intense light, deviations from this ideal can lead to suboptimal growth and may affect its vitality. In its outdoor habitat, amur Cork Tree is best situated in open spaces that receive unfiltered daylight for most of the day. It possesses a robust constitution but, like many plants, may experience stress or reduced vigor if exposed to prolonged shade. The plant’s canopy architecture is designed to maximize light absorption, contributing to its resilience in various light environments.
Watering
Originating from the temperate regions of East Asia, amur Cork Tree is adapted to withstand periods of lower moisture availability. This species thrives with a watering schedule that mimics its natural environment, necessitating hydration once every two weeks. As a deciduous plant, amur Cork Tree’s water needs fluctuate with the seasons; it requires less during dormancy in winter and more as new growth emerges in spring. Typically grown outdoors, amur Cork Tree can adapt to various soil conditions but flourishes when moisture is consistent yet not excessive, aligning with its moderate drought tolerance.
Fertilizing
For optimal health, amur Cork Tree requires balanced nutrition fertilizers in the growing season for robust growth and high nitrogen fertilizers during early development to establish foliage. Fertilize bi-annually, applying the recommended dose as per product guidelines, reducing quantity in dormant winter months. Fertilization enhances amur Cork Tree’s vigor, flowering, and resistance to pests. Avoid over-fertilization to protect root integrity. Seasonal variations influence nutrient needs; increase during spring growth, taper in fall. For effective uptake, water soil before application.
Propagation
Amur Cork Tree is a durable and adaptable tree grown for its ornamental qualities and medicinal value. Successful propagation mainly involves seed sowing. Seeds should be collected when ripe and sown immediately as they lose viability quickly. Stratification can enhance germination, but it’s not crucial. Softwood cuttings can also root but are less commonly used. Semi-hardwood cuttings taken in late summer yield better results if chosen as an alternate method.
Transplanting
The right moment for relocating amur Cork Tree is during the S1-S2 season due to reduced stress on the plant. Find a location with well-drained soil and plenty of sunlight. When transplanting, ensure to cover the root ball completely. Remember, amur Cork Tree thrives with care and patience.
III. Uses and Benefits
- Ornamental uses
Landscape tree for large lots or parks. Generally considered to be a poor street tree because of its spreading, low-branching habit.
- Medicinal uses
It has been used as a Chinese traditional medicine for the treatment of meningitis, bacillary dysentery, pneumonia, tuberculosis, tumours, jaundice and liver cirrhosis.
Used orally to treat abdominal pain, diarrhea, gastroenteritis and urinary tract infections. Phellodendron amurense may protect cartilage against osteoarthritis progression. It may prove to be a potentially important chemopreventive agent for lung cancer.
Phellodendron amurense is able to inhibit prostatic contractility suggesting that it may be useful in the treatment of urological disorders caused by prostatic urethral obstruction such as benign prostatic hyperplasia (BPH). Nexrutine (bark extract from Phellodendron amurense) may have potential to prevent prostate tumor development.
Compounds in the leaves (quercetin, quercetin-3-O-beta-D-glucoside, quercetin-3-O-beta-D-galactoside and kaempferol-3-O-beta-D-glucoside) demonstrated significant free radical scavenging activity comparable to vitamin E.
The tree has both antibiotic and antimicrobial properties due to the alkaloids contained within the plant material. The major chemical constituents of its bark are the isoquinoline alkaloids, palmatine, jatrorrhizine, phellodendorine with berberine found within the leaves. The indole alkaloid has also been found in the roots of the young dioecious trees.
Dye extracted from the bark was used historically across East Asia to color paper for sutras and other documents, including the Diamond Sutra. The yellow dye protected against insect damage.