Fact Sheet: Ecology and Control of Amur Corktree Phellodendron amurense Rupr. Background Amur corktree is native to Eastern Asia, including Northern China, Korea, and Japan. It was originally introduced in the U.S. in the 1850s, and is still being planted as an ornamental and street tree. It has been reported as invading sites in Illinois, Indiana, Massachusetts, New York, Pennsylvania, and Virginia. In Illinois, it has been reported as invasive in the northeast in Cook, DuPage, and Will Counties, and in Jackson County in southern Illinois (EDDMapS 2017), though it is likely underreported in the state. In southern Illinois, its known range has expanded in recent years, and has proliferated along forest edges and in storm-damaged areas of forest where it outcompetes native species, but recent research indicates it also persists in closed canopy forests as well. You can help by reporting sightings of this species to EDDMapS online or EDDMapS Midwest phone application. Identification and Ecology Amur corktrees are deciduous trees that, when mature, reach 35-50 feet in height and have thick corky bark that feels spongy to the touch. They have opposite, pinnately compound leaves with 5-13 leaflets with entire leaf margins. The leaves can resemble other tree species with similar compound leaves, such as the invasive tree of heaven, or native ash tree species. One way to differentiate between the Amur corktree and the potential lookalikes is by cutting off a piece of the outer bark. Beneath the outer bark, the inner bark is distinctively bright yellow. Also, corktree leaves tend to turn a lime-green to yellow color and they retain them a bit longer than a lot of the other canopy trees in the fall, so that can be a good time to locate them. Mature female trees produce abundant fruits 0.25-0.5 in. (0.6-1.3 cm) in diameter that are bright green and turn to black when they mature in June-July. The drupes (fruits) are readily consumed by birds which are then spread to new areas. Photo: Ansel Oommen, Bugwood.org Photo: Chris Evans, University of Illinois Extension, Bugwood.org Photo: Kevin Rohling, River to River CWMA Image and Data: EDDMapS 2017 Identification and Ecology Continued In the U.S., Amur corktree has been found invading forest edges, canopy gaps, and areas of human disturbance, but can also persist in the understory of closed-canopy forests. One study in New York found that corktree was able to invade forests with differing dominant overstory species, and different forest stand ages illustrating this species’ adaptability to varying site conditions. In addition, areas with overpopulations of deer may favor increases in corktree as deer tend to browse preferably on native tree species and are known to avoid browsing on corktree (Morgan and Borysiewicz 2012). Management Like most invasive plants, Amur corktree can best be controlled through an integrated pest management plan. Seedlings can be hand-pulled. Prescribed fire can be used to control seedlings, and prepare for other treatments, such as foliar application of herbicides on resprouts following top-kill by fire. Land managers in Illinois and New York have successfully treated Amur corktree using typical woody species herbicide treatments such as cut-stump, basal bark, and foliar herbicide applications. Those treatments include cut stump using glyphosate (50-100% v/v solution) or triclopyr ester (25% v/v solution). Also, basal bark methods using concentrated triclopyr ester (25% solution in bark oil carrier) are effective. Smaller stem plants can be treated with a foliar treatment of 5% v/v triclopyr amine or 2% v/v glyphosate while the plants are actively growing. For more information, please see the River to River Cooperative Weed Management Area website at www.rtrcwma.org or email us at [email protected] Author: Kevin Rohling, River to River Cooperative Weed Management Area Project Coordinator, June 2017 Editor: Chris Evans, University of Illinois Extension Forestry, Forestry Extension and Research Specialist Thank you to Illinois Forestry Development Council for their support for the creation of this fact sheet. References EDDMapS. 2017. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/; last accessed June 8, 2017. Glaeser, C. W. and D. Kincaid. 2005. The non-native invasive Phellodendron amurense Rupr. in a New York City Woodland. Arboricultural Journal. 28:151–164. Morgan, E.C. 2012. Stand dynamics of a 46-year invasion by Phellodendron amurense Rupr. in an Eastern North American Forest. Castanea. 77:21-27. Morgan, E.C. and J.A. Borysiewicz. 2012. The invasion of Phellodendron amurense into the urban and suburban woodlands of the New York City Region. Urban Habitats. Available online at http://www.urbanhabitats.org/v07n01/phellodendron_full.html; last accessed June 13, 2017. Simons, D. 2006. Fact Sheet: Amur Cork Tree. Plant Conservation Alliance®s Alien Plant Working Group. Available online at https://www.nps.gov/plants/alien/fact/pdf/pham1.pdf; last accessed June 13, 2017. Jacquart, E. 2012. Official Amur Corktree (Phellodendron amurense) assessment, Assessment of Invasive Species in Indiana’s Natural Areas. Available online at https://www.entm.purdue.edu/iisc/pdf/plants/Phellodendron_amurense.pdf; last accessed June 13, 2017. .