Those that have said buckthorn are correct. European Buckthorn is an exotic species from Europe brought to the US as decorative/ornamaental shrubs. As is with most exotic species, they usually thrive in their new home which is what Buckthorn has done in the US. Where I work, we work hard to control it with cutting and chemicals because it will literally take over a stand of timber shading out oak, hickory, walnut seedlings. It really does ruin a landscape. Unfortunately because deer WILL eat it (not preferred) and turkeys also eat the berries, it is virtually impossible to control the spread. Those of you in the northern climates, when you go out in November and there is one green tree left in the woods holding its leaves, thats buckthorn.