Tribulus terrestris is an annual plant in the caltrop family (Zygophyllaceae) widely distributed around the world. It is adapted to thrive in dry climate locations in which few other plants can survive. It is native to warm temperate and tropical regions in southern Eurasia and Africa. It has been unintentionally introduced to North America and Australia. An aggressive and hardy invasive species, T. terrestris is widely known as a noxious weed because of its small woody fruit – the bur – having long sharp and strong spines which easily penetrate surfaces, such as bare feet or thin shoes of crop workers and other pedestrians, the rubber of bicycle tires, and the mouths and skin of grazing animals. (Source: Wikipedia.org, CC BY-SA)