2008-12-03 P & R Packet - Laserfiche WebLink

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Of the two species of exotic buckthorn that have become established in Minnesota, the European or common buckthorn (Rhamnus cathartica) is the most widespread and problematic. Originally imported as an ornamental, it has not been sold since the 1930s, when it was found to be a carrier of oat crown rust, an oat disease. Garden centers sell the glossy or columnar alder-buckthorn (R. frangula) in several varieties-- including columnar and fernleaf--as a horticultural plant. Several Twin Cities nurseries have voluntarily stopped selling this tree because of its ability to escape cultivation. A problem in wetlands, glossy buckthorn will also spread into upland sites. European buckthorn has small alternate simple leaves, black berries, and a flaky bark. The side branches have short terminal spurs, or thoms, which are literally a pain if you try to remove the plant. Glossy buckthorn has leaves similar to those of European buckthorn, but it has smooth bark and no spurs. The fruits are less numerous than those of European buckthorn. During the summer, buckthorns sometimes resemble a number of small trees, including wild plum and some cherry trees. Fall is the easiest time to identify buckthorn. The leaves of buckthorns do not change color until late in the fall, after most other trees have changed. The berries usually stay on the branches until March. Many species of birds, especially robins and cedar waxwings, eat the plentiful blue-black berries and help spread them to other areas. Despite this effective means of spreading, more than 90 percent of the seeds land under the parent tree. The ground under mature buckthorn trees can have about 75 seeds per square foot. (In comparison, com is planted at less than five seeds per square foot.) High densities of seeds result in 15 to 20 seedlings per square foot or up to a half million per acre. Wood lots with this density of seedlings are a green carpet of buckthorn. At this level of infestation, not much else grows. Early Intervention Buckthorn in your back yard is most easily controlled before it spreads. If you have only one or two buckthorn trees, remove them right away. A large area with many trees to control presents a bigger problem. If you have more than five acres of buckthorn, contact your local resource manager for advice. The Department of Agriculture, Department of Natural Resources, Minneapolis Park Board, and Hennepin Parks all have undertaken large-scale control programs on their properties. Control of buckthorn in large heavily infested areas is not yet economically feasible. Several state and regional agencies are beginning to research control methods, including biological control, which uses other organisms to eliminate or reduce the problem species population. Buckthorn Removal Here are the basic steps for removing buckthorn on your property: 1. Cut down all buckthorn trees greater than 3 inches in diameter. Buckthorns of this size produce berries. A handsaw works well, but a chain saw is more efficient if you have many trees to remove.