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DNR SEEKS PUBLIC HELP TO IDENTIFY AND MAP INVASIVE CORK TREES

Contact(s): Mike Putnam, DNR forest invasive plant coordinator, 608-843-5475; Michael.Putnam@wisconsin.gov
February 26, 2019

MADISON -- Wisconsin invasive species officials are asking the public to help identify and locate populations of the invasive Amur cork tree.

The Wisconsin Department of Natural Resources has records of Amur cork tree in at least 12 counties with individual populations ranging from a single tree to several thousand. It is possible this number will increase with improved mapping efforts. The species, prohibited under Wisconsin's invasive species rule, is harmful to diversity in forested communities.

Often planted in parks, yards and cities, Amur cork tree can quickly invade forests when its fruits are eaten and dispersed by birds. Dense mats of seedlings can stop the growth of native plants and harm wildlife populations that depend on them.

Amur cork tree's listing as a prohibited species is unique because female trees are regulated but male cultivars and seedling stock, which were thought to be unable to produce fruit, are not. There is some indication, however, that trees previously thought to be fruitless may produce fruit.

To identify this species in the winter, look for the signature corky outer bark or the bright yellow cambium (tissue just beneath the bark). Use a knife to peel away the thinner bark on branches or cut into the corky bark on larger trees using a small axe. Winter buds and fruits can also be used for identification. Winter buds are reddish brown and encircled by a horseshoe-shaped leaf scar. The fruits are black when fully ripe and remain on trees into winter. Even after the fruits have fallen or been eaten by birds, spiky stems can be seen still attached to the upper branches of the tree. Pictures of these features can be seen in the invasive species photo gallery on the DNR website.

If you know of possible locations of this species in Wisconsin, you can email invasive.species@wisconsin.gov with the subject line "Amur cork tree location." Please include a street address and coordinates (use this site to pinpoint a location) and photos of characteristic features described above. Photos of fruiting structures (fruits, stems) are especially helpful in finding the trees that contribute most to the spread of this species.

For more information about Amur cork tree, including details on identification and a map of known populations, search the DNR website, dnr.wi.gov, for Amur cork tree. If you would like to know more about funding options to control this species on your property, please contact Mike Putnam, DNR Forest Invasive Plant Coordinator, at Michael.Putnam@wisconsin.gov or 608-843-5475.