On May 4, 2004 Dan Ernst (DNR Cooperative Forest Management Supervisor) and I completed the annual  monitoring of the Corning Forest Legacy Conservation Easement. The easement was granted to the State of Indiana in 2001, and the property has been a Classified Forest since 1983. Fifteen minutes into our hike, we discovered a couple of small trees we did not recognize. The leaves and branch pattern resembled an ash, but the bark was definitely different from any ash we knew. We continued our tour of the 136-acre property, and as luck would have it, we did not encounter the species again that day. Most of our monitoring work was spent documenting boundary information in relatively undisturbed portions of the tract.

A few days later, though, curiosity brought me back to the site of the unknown trees. I gathered leaf specimens and made mental notes of the trees characteristics. The base of the petiole nearly enclosed the lateral buds, and there did not appear to be any terminal buds. The petiole had an orange tinge unlike the purple usually associated with ash leaves. I looked over areas of the tract Dan and I hadn’t visited earlier. I found that there weren’t just two trees. There were several dozens of them, ranging in size from small seedlings up to 10-inch diameter trees at breast height. Most of the seedlings, saplings, and trees were scattered through woods and appeared to be associated with a timber harvest area. The woodland had been cut in 2000 after a severe drought damaged many Tulip trees the year before. Where there was a gap in the main canopy, several saplings usually occurred. In more shaded areas, seedlings were present in the understory. The largest trees occurred in the row of a 1970s-era tree plantation and they seemed to be intentionally planted with a few Norway spruce and a Chinese elm in what I call “exotic row”. Most of the plantation was white pine, which is not native to Southeast Indiana either, but apparently a few odd things had been planted in one corner as sort of an experiment. The intent or the source of the unusual trees is not known.

One day while thumbing through Dirr’s Manual of Woody Landscaping Plants, I came upon a possibility. Was it Amur cork tree? I returned to the site several more times during the growing season to look for flowers or fruit. Finally, I found developing drupes that later turned black as Dirr had described. The flowers are very small and easily overlooked. I announced to Dan and Phil O’Conner, our Tree Improvement Specialist, the results of my investigation. Phil directed me to The Nature Conservancy’s Invasive Species Initiative web site. Everything seemed to match – the unknown tree was Phellodendron amurense. An unexpected outcome was that Phil was trying to identify an unknown species at Clark State Forest at the same time, which turned out to be Amur cork tree also. We don’t know how the trees were introduced at either sites or why. But they are obviously very invasive. And although some sources label Amur cork tree as a medium-sized tree, it was competing nicely with the other species it was planted with. It also grows as fast as Tulip trees, and that’s pretty fast.

Part of my assignment for the Corning easement was to develop a Forest Stewardship Plan. I decided to include a section on invasive species and actually listed seven that I knew. Mr. Corning was alive when I first wrote the plan in 2004, and he agreed to follow my recommendations including to control invasive species. However, he asked if he could wait until cost-share funding could be secured. Unfortunately, Mr. Corning died the following year. When Mr. Corning passed away, Gary Conant, a close friend of the family and the former RC&D Director, offered to help Mrs. Corning. He was granted power-of-attorney for the property. I met with Gary in late 2006 to discuss the management of the property shortly after the establishment of the Indiana Woodland Restoration Program. I suggested doing two invasive species control projects, one for trees and one for shrubs. After consulting with Mrs. Corning, Gary applied for the two projects in January of 2007.

Both projects, Invasive Tree Species Colony Control and Invasive Shrub Species Control were approved later that year. Both projects were initially slated for 41 acres, the combined acreage of two areas described in the Woodland Stewardship Plan. The cork tree project area was later reduced to 33 acres, because the invasive trees were absent on some of the initial area.

The next step was to look for a contractor to complete the project. I suggested asking the Woodland Committee of the Historic Hoosier Hills Resource Conservation and Development Area (RC&D) if they wanted to work on the project as a fund-raiser. Gary thought that Mr. Corning would like that suggestion. At the Woodland Committee’s spring banquet, I made a proposal that the committee take on the project. It was tabled until the summer planning meeting, but it was ultimately adopted.

I spent several days during the summer of 2007 locating and marking Amur cork tree seedlings, saplings, and trees with blue tree marking paint. It took 35 man hours to do the marking including travel time for the six trips. On the same day as the fall banquet in September, I lead a tour to the Corning property to discuss invasive species issues including Amur cork tree.

Finally, several members of the committee met at the Corning property on October 7, 2007 to cut and treat as many cork trees as possible. The herbicide of choice was Pathway RTU, which was applied to chainsaw girdles and to cut stumps. Approximately 42 person-hours were spent on the property that day without counting travel time, which would be at least 7 hours. The work went fairly quickly since the trees were marked, although we were fighting heavy multiflora rose over much of the area. I estimate the total number of Amur cork trees to be close to 1000 although a 100% tally was not done. The workers included Rob McGriff (District Forester), Joe Schuerman (Consulting Forester), Steve Doll (Consulting Forester), Rosemary Bolenbaugh (Jennings County Landowner), Dick Jones (Jefferson County Landowner), myself, and one of Joe’s workers. In addition to treating the Corning property, several cork trees on the adjoining property south and east of Corning’s were cut and treated. Subsequently, I have made three more trips to the property to search for missed seedlings and have spent 6? hours finding, cutting, and treating them (about 50 seedlings). Although they were marked with blue paint, they are easy to walk past without being seen. I am confident now that all the marked cork trees were cut and treated. Future monitoring will determine how well we did at our control efforts.

The total amount of time spent on the Amur cork tree project over the 33-acre treatment area was 90 ? hours including travel (41 ? hours of this total was marking and follow-up treatment). Initial planning time is not included. The incentive funding from IWRP was $75 per acre or $2,475 total. The Woodland Committee, of which I am a member, made $27.35 per hour of time spent on the project. This figure is before deducting herbicide and equipment costs, which were minimal or donated in this case.

It is possible that future work will need to be done if new seedlings germinate or if more missed seedlings, saplings, or trees are found. A search of surrounding properties would be beneficial to make sure the population was eliminated from the area, but that will depend on available time and getting permission from the individual landowners to do so. The problem is: how far is it possible for a bird fly before it deposits seeds in a suitable location? I doubt anyone knows the answer. It will take years to find out if this project was a complete success, but we know the original seed source of this introduced and invasive species has been eliminated. But, somewhere on the landscape could be additional trees ready to produce seed and invade new sites unchecked. That is why we need to know our native trees and be curious about ones we do not know. An unknown tree could be an invasive species that could compete with or replace our native trees.

Darrell Breedlove is a District Forester with the IDNR Division of Forestry.