Now winter is passing snowdrops and crocuses are brightening the ground beneath the trees in the parks but all year round we can see the beautiful blue-grey, golden and rust orange of lichens on trees and stones, on city walls and in woodland. These extraordinary life forms are a symbiotic union of a fungus and a partner, often an alga, that produces energy through photosynthesis.
Britain has over 1500 lichen types and many live to a great age. The oldest known in this country live on the Rollright stone circle near Oxford. We visited the circle on a frosty day and the place looked enchanted.
The lichen at Rollright, Aspicilia calcarea, is estimated to have begun its life around 1195 AD. It’s the white lichen in the middle photo (I think). See also here: