A country churchyard, left largely to itself for two or three hundred years, is one of the richest hunting grounds a moss-watcher has. Nowhere else in the lowland landscape offers so much old, undisturbed stone, cut from so many different rocks, set at so many angles to the sun. Bryologists have long known it, and a single well-worn burial ground can hold more kinds of moss than the farmland for a mile around.
A sanctuary of old stone
Several things conspire to make the churchyard so hospitable. Its stones have stood still for generations, and moss, slow to arrive and slower to build a cushion, is repaid for that constancy. The masons drew their materials from wherever they could, so one yard may set acid sandstone headstones beside limestone chest tombs, granite kerbs and beds of lime mortar, each a separate world for plants that are fussy about lime. The harsh sprays that scour a garden path seldom reach the quieter corners, and the grass is cut but rarely dug. Fold in the deep shade under an old yew and the baking crown of a south-facing tomb, and you have a spread of conditions no ordinary garden can rival.
On the tombs themselves
Sunlit stone, dry and bright for much of the day, favours the tough hoary specialists. The little grey domes that stud the shoulders of many an old headstone, their leaf-tips drawn out into white hairs, are pincushion mosses, perfectly at ease in the heat and drought, and given their own account in common pincushion. Wall screw-moss, its leaves curling into corkscrews as they dry, settles on mortar and softer limestone and appears so faithfully on churchyard walls that it has become almost their emblem; there is more on it in wall screw-moss. On limestone in good light you may catch the silky, golden wefts of feather-mosses that gleam near bronze in low sun, while the plain grey-green of silvery thread-moss works into every joint and hairline crack, the same weedy survivor met on pavements in silvery thread-moss.
North faces and shaded ground
Step round to the cold north side of a stone, or in under the churchyard trees, and the cast changes entirely. Damp, shaded stone grows a softer, greener fur, the mat-forming feather-mosses that also drape woodland banks, and on the ground between the graves the taller turf-mosses and broad green carpets take over from the drought-hardened cushions of the sunlit faces. This is why one tomb can wear two quite different mosses on its two sides, and why walking a churchyard slowly, from the bright southern wall round to the shadowed north, teaches you more about how aspect rules a moss than any book will.
Reading the stone
With a little practice the moss becomes a way of reading the stone beneath it. A headstone cushioned in lime-loving species is very likely limestone, or bedded in mortar; one that carries only acid-tolerant mosses is probably sandstone or granite. Because the rock decides so much, churchyards have become a favoured place to record bryophytes, and patient surveys have logged well past a hundred species in some of the older Welsh and West Country yards. It makes an ideal classroom, since the same handful of stone-dwellers recurs from yard to yard until they are old friends; the general method is laid out in how to identify a moss.
Green stone and fading names
The moss does pose a real tension, for a thick green pelt can swallow an inscription and, across long years, quicken the weathering of soft stone. Families and conservators sometimes wish it gone. Yet historic stone is easily wrecked by rough cleaning: wire brushes, pressure washers and the fierce chemicals sold for patios bite into the surface and carry the carving off with them, doing far more lasting harm than the moss ever would. Where a name genuinely must be read again, the lightest touch is the right one, a soft brush and plain water and nothing sterner, ideally on the advice of someone who knows the stone; the broader case against scrubbing runs through removing moss. On most graves, letting the green stay is the kinder and wiser choice.
A walk worth taking
You need little for this beyond a hand lens and an unhurried hour. Pick an old churchyard, begin at the sunniest wall and work round towards the shade, and watch the mosses hand over from one community to the next as the light and the rock change. Tread gently among the graves, take nothing but a photograph, and keep in mind that the ground is a resting place before it is anything else.