Viola lutea var. westfalica

Viola lutea var. westfalica, also known as high calamine pansy, Westphalia pansy, or zinc pansy, is a variety of violet native to Westphalia, Germany. It is found in the wild only in the districts of Paderborn, Hoexter and Hochsauerlandkreis, although it is cultivated in other locations. These are industrial areas where much of the soil is contaminated with lead, zinc and other metals, which some Viola species are more able to tolerate than some other plants....read more on Wikipedia.