Though lichens are generally intolerant of pollution, this vibrant yellow and orange beauty is an exception and is even tolerant of heavy metal contamination. Its common names include common orange lichen, yellow scale, maritime sunburst lichen and shore lichen, from which you might correctly deduce that Xanthoria parietina is just as common on a rock at the seaside as it is on a tree in the city. It is also something of a globetrotter, being found throughout Britain and most of Europe, in North America, Africa and Asia, as well as in Australia.
Working from the belief that a plant could treat a disease it most looked like, medieval herbalists used Xanthoria parietina to treat jaundice because of its yellow colour, and scientific research has since shown that it has potent antiviral properties. And, given the intense yellow and orange colours of this lichen, it’s probably no surprise to learn that it has also been used as a dye. It is, for example, one of the traditional plant materials used to dye wool in the Scottish highlands and islands, though the colour it produces is brown, not yellow.