A few years ago, I was on an early morning hike in a local Ohio hardwood forest. Surrounded by gigantic sugar maples and stately beech, I felt like I was being hugged by friendly giants. As I continued to meander up the trail, I came across a tree I didn’t recognize. With a relatively short & stocky trunk, large, broadly spreading branches, and a distinctly corky bark, the tree appeared to be taking advantage of a large gap in the canopy. I ambled over for a closer look.
I was thrown for a loop when I saw it had an opposite branching pattern and oppositely arranged pinnately compound leaves on its thick branches that lacked terminal buds. And like ornaments on a tree, it was adorned with clusters of small black drupes in terminal panicles. I went through the short checklist of trees I knew with this opposite branching habit…and none fit the bill! Though I was perplexed, I was also a wee bit excited: I do love a good game of “Name that Tree.” I scratched my head and looked around for other clues.
I quickly noticed that I was encircled by an abundance of small saplings that looked like miniature versions of this behemoth. They didn’t seem to overly perturbed by the heavy shade cast upon them by the surrounding maples. The sheer quantity of progeny from what I assumed might very well be this parent tree, made me a bit uneasy. I took out my trusty pocketknife and nicked the bark of one of the saplings and was struck when I noticed a bright yellow inner bark. I’m talking, mustard-stain-on-a-white-tee-shirt yellow. Like a good detective, I took my evidence back to my office and began my investigation.
It wasn’t long before I was able to narrow down my culprit to Phellodendron amurense, Amur corktree. Native to Eastern Asia, Amur corktree was first introduced in the 1850s as an ornamental. Growing to a height of 35-45 feet, this deciduous tree is dioecious, meaning that female and male flowers occur on separate trees. As such, trees with female flowers pose the larger risk for spread due to birds consuming and dispersing their seeds.
Amur corktree appears on invasive species lists of several northern Midwestern states including Pennsylvania, Indiana, Kentucky, Wisconsin, Minnesota, as well as several New England states. According to EDDMaps, “This tree is demonstrating invasive characteristics in suburban and urban fringe forests. It escapes intended plantings to invade and displace native hardwood forests.”
What do you do if you come across Amur corktree on your next hike? First, make its presence known! Use the Great Lakes Early Detection Network (GLEDN) app to report your sighting. According to EDDMaps, Amur corktree is already known to occur in eight Ohio counties. It can be controlled using the same methods that apply to other invasive tree species. Small seedlings can be pulled from moist soil. Cut stump treatment, girdling, and foliar treatments are all options for larger trees, and herbicides should be carefully selected based on the time of year and the site conditions. Contact your local Extension office for more information on Amur corktree management.
