Lichens
are fascinating organisms. A double whammy of two "plants" in one: a fungus,
which is the visible part, and an alga, which protected by the fungus, provides
food from sunlight in the same way as green plants. Lichens grow slowly and
are long-lived, some as old as the gravestones themselves.
In St Mary's churchyard seventeen different lichens have been recorded, one of which, Collema crispum, grows in the damp recesses of the cross steps and is described by a lichenologist as "of particular interest". A walk round the churchyard will soon show you that local limestone is far more conducive to lichen growth than modern, highly polished, imported stone. Very often the older the tombstone the more lichens. One stone at St Mary's has six species on it. The British Lichen Society suggests that old tombstones should be left in situ so that the lichens remain undisturbed. If tombstones must be cleaned the Society recommends a soft brush and plain water. Yatton Local History Society has been recording tombstone inscriptions and this record will remove the need to disturb lichens for family historians.
Some moth caterpillars feed on lichen, for example the Marbled Beauty. I find it amazing that even on the gravestones which remember the dead, the complex web of life which we are trying to conserve is evident. Faith Moulin