In unpolluted churchyards, lichens often form mosaics of colour, especially on the stonework, adding to the character and interest of the site. They vary in form from simple, powdery scatterings and crusts to more elaborate leafy or even bushy structures. Contrary to popular opinion, lichens do not 'feed' on the stone, bark or soil upon which they grow. They reproduce by means of microscopic spores capable, on finding a suitable algal partner, of colonising most surfaces which are reasonably stable and not too shaded or smooth. Lichens may also propagate themselves by means of powdery outgrowths, minute projections or fragments which are scattered in the wind and rain or dispersed by small creatures.
Churchyards provide an excellent environment for the study of lichen biology and colonisation.
Of the 1700 British species, over 300 have been found growing on churchyard stone in lowland England. Almost half the species are rare, having been noted in fewer than ten churchyards. Some seldom occur in any other habitat. Many churchyards are found to have well over 100 species. They grow very slowly, sometimes no more than half a millimetre a year, and many are long-lived.