Amur Corktree (Invasive Plants of Maryland)

Amur Corktree

Phellodendron amurense

Description ¹⁰

Amur corktree is native to eastern Asia including Northern China (Manchuria, Ussuri, Amur), Korea, and Japan and was introduced into the United States in 1856 for ornamental purposes. To date, it has been reported to be invasive in scattered locations in Illinois, Maryland, Massachusetts, New York, Pennsylvania and Virginia. It prefers full sun and rich soils. Once established, it can form patches that displace native plants. It spreads by seed which is produced in abundance. Amur corktree can reach 35-45 ft. at maturity. The distinctive bark is a light golden brown on younger trees and gray-brown, ridged, and furrowed on mature trees. Bark of both young and old trees is slightly spongy or corky to the touch and has a distinctive bright neon yellow layer of inner bark that can be revealed with a quick scrape of a pocket-knife. The leaves are 10-15 in. long, opposite, pinnately compound with 5-11 (up to 13) entire leaflets that are dark green, turning bright yellow in the fall. When crushed, the leaves have a distinctive citrusy smell sometimes likened to a disinfectant or skunk odor. Male and female plants are separate (dioecious) and each bears hanging panicles of yellowish-green flowers from May through June. From mid-June to mid-July, female trees produce abundant clusters of fruits (technically drupes) which are ¼-½ in. diameter. The fruits bright are green, turning black in late summer to fall, and may remain on the tree until winter. It is a plant to watch and should be controlled as necessary.

Ecological threat in the united states ¹¹

Amur corktree outcompetes native tree and shrub species including oaks and hickories in forested natural areas. It may inhibit and suppress regeneration of overstory canopy trees. Corktree's effect on eastern American forest communities does not depend on the health and growth of individual large trees but on the great number of small ones. Oaks and hickories provide a nutritious fat-containing nut for wildlife that remains available through the winter, whereas corktree provides sugary berries that are lower in nutritional value. Many birds and mammals are dependant on oaks and hickories for food, including grackles, turkey, grouse, quail, blue jays, woodpeckers, waterfowl, deer, bear, squirrels, mice, rabbits, foxes, and raccoons. Because wildlife populations vary with the availability of acorns, populations of acorn-dependent species decrease in forests where Amur corktree has become established.

Amur corktree is invasive in parks and natural areas in New York City, New York and Philadelphia, Pennsylvania, where it has escaped from plantings. Within fifty years of its planting as an ornamental, it has become a dominant tree in New York City parks. The establishment and spread of corktree at three Audubon wildlife sanctuaries in eastern Massachusetts has been documented. It does especially well in forests and wooded areas that have been exposed to human disturbance, where it forms dense stands and crowds out native species. Corktree changes the light regime of forest understory with shelf-like branching that shades out seedlings of competing species. The high volume of seed produced and relative lack of seed predators gives it an additional competitive advantage over native species.