Rhamnus cathartica

About

Rhamnus cathartica, the European buckthorn, common buckthorn, purging buckthorn, or just buckthorn, is a species of small tree in the flowering plant family Rhamnaceae. It is native to Europe, northwest Africa and western Asia, from the central British Isles south to Morocco, and east to Kyrgyzstan. It was introduced to North America as an ornamental shrub in the early 19th century, and is now naturalized and classified as an invasive species in the northern United States and Canada from Saskatchewan to Nova Scotia.

Summary from Wikipedia