Rhamnus cathartica aka Common Buckthorn

Rhamnus cathartica, also known as the European buckthorn, common buckthorn, or purging buckthorn, is a small tree or shrub in the Rhamnaceae family. It is native to Europe, northwest Africa, and western Asia, but was introduced to North America in the early 19th century as an ornamental shrub. It has since become naturalized in various locations, primarily extending from Nova Scotia to Saskatchewan, south to Missouri and Virginia. While it is easy to grow as a houseplant, it is considered an invasive species in several US states and in Ontario, Canada. The common buckthorn is a thicket-forming deciduous shrub or small tree that can grow up to 25 feet tall. Its leaves are elliptic to oval, mostly subopposite, dark green, and toothed with 3-5 pairs of veins. The leaves retain their green color long into fall but eventually turn yellow. Small yellow-green flowers bloom in spring (April-June). This buckthorn is also noted for having small spines at the branchlet ends. It prefers long-lasting, direct light and should be less than one foot from a window. Regular watering is necessary for its growth, but it does not require added fertilizers if repotted each time it doubles in size. Common Buckthorn belongs to the Rhamnus genus and is native to Europe, Western Siberia, Northwest China, and Northwestern Africa.