Hi Adam: The invasiveness of Buckthorn apparently is somehow related to the proximity of Lake Michigan. The closer to the lake the worse the problem becomes. On the other hand, downstate where the temps are milder, like near the lake front, the buckthorn is not a problem. The remainder of zone 5 to the east and west of this region is also apparently free of buckthorn gone wild. A complex issue at best. The more we learn the more we understand how little we know. The open sharing of knowledge, not simply information on this listserve provides for continuous learning which is one of the reasons why I enjoy Pacific Bulb Society so much. It keeps me young and provides almost constant opportunities to look at the plant world with a slightly different perspective every day. Boyce Tankersley Director of Living Plant Documentation Chicago Botanic Garden 1000 Lake Cook Road Glencoe, IL 60022 tel: 847-835-6841 fax: 847-835-1635 email: btankers@chicagobotanic.org