Sempervivum tectorum L. Crassulaceae Houseleek, Senegreene Distribution: Europe. Sempervivum means 'live forever', tectorum means 'roof', and was apparently grown on house roofs to protect against lightning. Lyte (1578 distinguishes Stonecrops (Sedum) from Sengreene (Sempervivum) for he advises the latter, alone or mixed with barley meal, applied topically to burns, scalds, St Anthony's fire [erysipelas] , ulcers and sores, will cure them and sore eyes. Apropos of stonecrops (Sedum), he describes the redness and blistering that the sap has on bare skin, and how it is good for poisons for if taken with vinegar by mouth it causes vomiting, but only safe to do so in strong people. He seems fairly confused as to which is which. Not approved by the European Medicines Agency for Traditional Herbal Medicinal use. Photographed in the Medicinal Garden of the Royal College of Physicians, London.