What is this tree with black berries?

Q: Can you identify the plant in the photo? It s a bushy tree that s about 10 to 15 feet tall. The berries are numerous, even this late in the season. – Dennis H. A: The tree is Common Buckthorn, which has the botanical name Rhamnus cathartica, and it s a highly invasive species. It was brought into the United States as a landscape plant in the 1800s, mostly for use in tall hedges and has since escaped, becoming a nuisance with serious consequences. Buckthorn forms a shrubby tree reaching a height of 15 to 25 feet. It produces blackish colored berries containing seeds. Bird consume the berries, which act as a laxative, and seeds are spread as birds travel. Buckthorn crowds out native and desirable tree and shrub species, creating a massive buckthorn thicket, causing Minnesota to place the species on its noxious weeds list. Buckthorn can be identified by the prominent veins on the egg-shaped leaves and the buck hoof print seen at the end of twigs, formed by two ter