Wall Pennywort: The Plant of the Old Stone Walls
On old stone walls in the damper parts of the country, wall pennywort pushes out from the mortar in May. It is a small fleshy plant with round, succulent, shallow-cupped leaves the size of a five-pence piece, sitting flat against the stone in dense colonies. Cornish in particular but Devon and the Welsh borders too. The Latin name is Umbilicus rupestris, the navel of the rock, and that name carries the plant's old folk use and a slightly improbable medical tradition with it.
Identifying
The leaves are circular and almost flat, three to five centimetres across, with a small dimple in the centre where the stalk attaches to the underside, giving the leaf the look of a navel or a flat-cup mushroom. The plant grows directly from cracks in mortar or rock, often in colonies of fifty or sixty rosettes packed close together. In May and June it sends up an upright spike of small bell-shaped greenish-white flowers, twenty to thirty centimetres tall, opening from the bottom upward. The plant is in leaf year-round but the flower spike is the May feature.
The names
The Cornish name is penny-pie, after the shape of the leaf, and Cornish children ate the leaves raw on the way home from school. Mild, juicy, faintly cucumber-flavoured, not unlike a flat version of purslane. The other common name is navelwort, after the dimple in the leaf, and the older folk use was as direct as the name suggests. Country mothers across the West Country pressed a fresh leaf, dimple-down, against the navel of an infant who had developed a hernia or an umbilical rupture, on the principle that the plant shaped like the part of the body was the one for the job. The practice was recorded into the early twentieth century by Charlotte Latham among others.
The doctrine of signatures
The logic was the doctrine of signatures, a medical theory popular in early modern Europe holding that a plant shaped like a part of the body was put there by God for the treatment of that part. Walnuts for the brain, eyebright for the eye, liverwort for the liver, navelwort for the navel. The doctrine fell out of medical use in the seventeenth century, but folk uses based on it survived for another two hundred years in country practice. Whether the leaf actually helped an umbilical hernia is another question; that the mothers reached for it first is not in doubt.
Culpeper 1653
Nicholas Culpeper in his Complete Herbal of 1653 set down the broader use as a cooling poultice for inflamed skin. The leaves are over ninety per cent water, and the cell walls hold the moisture against the skin in a way a wet cloth does not. Culpeper recommended pennywort for "hot pustules and inflammations of the skin" and for "kibed heels" – the old name for chilblains – with a method that has not changed in three hundred and seventy years. Bruise the leaves to release the juice, lay them dimple-down on the inflamed skin, hold in place for ten minutes, repeat with fresh leaves three or four times a day.
Where it grows
Wall pennywort is a plant of damp air and old masonry. It needs a long enough growing season for the leaves to develop, year-round humidity high enough that the mortar stays slightly damp, and a stone or mortar substrate it can root into. The combination is found mostly in Cornwall, Devon, west Somerset, the southern Welsh marches, parts of Pembrokeshire, the Lake District, and west Scotland. East of a line from the Severn to the Wash the plant becomes increasingly scarce, then absent. The Atlantic side of the country has it; the continental side does not.
Sources: Nicholas Culpeper, Complete Herbal (1653); Charlotte Latham, Some West Sussex Superstitions Lingering in 1868 (1878); Plantlife species note: Umbilicus rupestris; Geoffrey Grigson, The Englishman's Flora (1958).