Something like half of our medicines are based on chemicals found in plants, and researchers have – sometimes controversially – scoured remote areas of the world for wild plants with therapeutic potential.

However, as David Allen and Gabrielle Hatfield document in a recently published book, there could be botanical riches much closer to home. ‘Medicinal Plants in Folk Tradition: An ethnobotany of Britain and Ireland’ for the first time collates fragmentary information about the traditional uses of herbs into one resource.

The book shows that the folk medical tradition was impressively wide in its botanical reach. “At a rough guess, a half of all native species were utilised,” says Dr Allen.

So why has this rich tradition been overlooked? “Historians of medicine have tended to rely on texts to reconstruct the past,” says Dr Allen. “This has led them to overlook, or at least underrate, the amount of lore shared and passed on through centuries among the illiterate, which has tended to be dismissed as merely learned medicine garbled or misunderstood.”

This is a misconception, argue Dr Allen and Dr Hatfield. The evidence, they suggest, is of a distinct herbal tradition that owed little to writing – and was based on its own botanical repertoire. Learned medicine in the West developed from Graeco-Roman traditions. But the Greeks and Romans had little or no knowledge of what grew in northern Europe.

Although learned practitioners were contemptuous of ‘hedgerow’ medicine, local herbal remedies would probably have been more helpful, andless harmful, than the classical practices of burning and bleeding. Medical men were also more likely to look overseas for their materia medica: exotic ingredients could be used to justify the premium prices they charged their affluent customers.

However, the opening up of the globe to trade did encourage people to look more closely at the plants in their own back yards. In 1695, a survey of Scotland’s Western Isles was initiated partly to this end by physicians in Edinburgh. For the next 200 years or so, interest was sustained mainly by physicians with botanic training and collectors of rural folklore.

But the folk tradition remained marginal. Its profile dropped still further as more and more exotic species began to be imported to these shores, as explorers ventured into new lands and collected new specimens.

A major change occurred in the 1930s. The Irish government, encouraged by the Celtic revival, instigated a movement to recover folk beliefs and practices. The Schools Survey was carried out by children in every primary school, who were given a questionnaire with which to interview local elderly people. The results, beautifully written out, were then compiled into over 1100 volumes and stored in the Department of Irish Folklore at University College Dublin. A leading Irish field botanist, Sylvia Reynolds, spent six months combing through this remarkable archive.

These findings, together with fragmented information from manuscripts and archives scattered across the British Isles, reveal considerable discrepancies in the way plants were used in different places. For example, goosegrass and watercress were used widely in Ireland but rarely in England.

Sometimes the same plant had different uses: herb robert was used for skin troubles in England and for coughs or kidney complaints in Ireland. Holly leaves were used exclusively in England for chilblains. Perhaps, suggests Dr Allen, the English found chilblains particularly troublesome, or the climate or diet might have made them more common.

David Allen