Toothwort and toothache: a botanical old wive's tale.

Thursday's Guardian Country Diary concerns toothwort Lathraea squamaria, the parasitic flowering plant that depends entirely on hazel trees for its nutrition, since it is a plant without chlorophyll.

There is no hint of the plant's presence until March, when its scaly flowering shoots, which look quite reptilian and menacing, erupt through the soil.

They're attached to hazel roots and some, like those in the picture above, can appear in grass some distance away from the trees, revealing how far hazel roots extend underground. 

After a brief flowering period, during which they attract bumblebee pollinators, the flowering  shoots soon set seeds and then by early summer they wither away.

Almost every wild flower book that I've ever read explains that the plant's common name arose from the appearance of  its flowers, which resemble rows of discoloured teeth, and then go on to suggest that it acquired its name via the Doctrine of Signatures. This fanciful notion, which dates back to Roman times and the physician Dioscorides, claimed that plants to look like a part of the human body will cure that organ's ailments. So with it's toothy appearance, toothwort must surely be a cure for toothache....... 

...... but there seems to be no evidence that anyone ever tried to use the plant in that capacity. In their scholarly work Medicinal Plants in Folk Tradition (2004) David E.Allen and Gabrielle Hatfield could only find one slight reference, in Gerard's Herbal, to a medicinal use for the plant and that was to treat lung complaints. It seems that the use of toothwort in folk medicine for dental self-medication is one of those plausible myths that never dies but is endlessly repeated.

The Doctrine of Signatures owes much to the German botanist Phillipus Aureolus Theophrastus Bombastus von Hohenheim (1493-1541) who, unsurprisingly, is best known by his shortened, Latinised name: Paracelsus. He refined the concept and it was later taken to absurd lengths by the English herbalist William Coles (1626-62), whose book Adam in Eden, or Nature's Paradise, woven together religion and botany, claiming that God created plants to look like body organs in order to signify their medicinal virtues to humans, extending the Doctrine far beyond the limits of credulity for all but the most devout.

Tears, Toothache and a Defunct Doctrine...

Inspired by a post on Rob's fascinating Wight Rambles blog, we went to look for toothwort - a weird, leafless, parasitic flowering plant devoid of chlorophyll that satisfies all its water and nutritional requirements by tapping into the roots of hazel: a vegetable vampire. We found it growing along the banks of the river Wear near Wolsingham, newly emerged from the soil.

I remembered reading the following in Charles Darwin's The Power of Movement in Plants, published in 1880:

'The passage of the flower-stem of the Lathraea through the ground cannot fail to be greatly facilitated by the extraordinary quantity of water secreted at this period of the year by the subterranean scale-like leaves; not that there is any reason to suppose that the secretion is a special adaptation for this purpose: it probably follows from the great quantity of sap absorbed in the early spring by the parasitic roots. After a long period without any rain, the earth had become light-coloured and very dry, but it was dark-coloured and damp, even in parts quite wet, for a distance of at least six inches all round each flower-stem. The water is secreted by glands which line the longitudinal channels running through each scale-like leaf.'

Sure enough the soil immediately around our newly-emerged flowering shoots was soaking wet, even though it was dry all around, just as Darwin had described 130 years ago. It may be that the plant has to secrete water in this way to maintain a flow of nutrient-laden liquid through its stems. Normal plants with leaves use the evaporation of water from the leaf surface to 'pull' the flow of water through - toothwort has to secrete 'tears' to achieve the same ends...

Folklore has it that toothwort acquired its common name as a result of the ancient Doctrine of Signatures, whereby plants that looked like parts of the human body were considered to have been designed in that way as an sign from the almighty that they could be used for healing the afflicted part of the anatomy. Toothwort flowers do look like rows of discoloured teeth. The plant only appears above ground for a couple of months in spring; I guess that there must have been a time when entrepreneurial apothecaries would have laid in supplies now, for treating toothache when the fresh plant wasn't available ....