Sherardia arvensis

Sherardia is a monotypic genus of flowering plants in the family Rubiaceae. The genus contains only one species, Sherardia arvensis, the (blue) field madder, which is widespread across most of Europe and northern Africa as well as southwest and central Asia (from Turkey to Saudi Arabia to Kazakhstan) and Macaronesia (Canary Islands, Azores, Madeira, Savage Islands). It is also reportedly naturalized in Australia, New Zealand, Taiwan, Kerguelen, Ethiopia, Sudan, southern Africa, Mexico, Costa Rica, South America, Bermuda, Cuba, Haiti and much of Canada and the United States (especially the Pacific States and the lower Mississippi Valley)....read more on Wikipedia.