Senna corymbosa (Lam.)H.S.Irwin&Barneby Caesalpinaceae. Argentine Senna. Distribution: Argentine (other species from Europe). This beautiful shrub that flowers from midsummer until the frosts of winter, is the source of one of the best known of all herbal medicines – Senokot (and senna pods and senna tea), introduced to European medicine (as Senna alexandrina from Egypt) by the Arabians. Every part of the plant contains anthraquinones which, if taken internally, act as a powerful laxative to treat constipation by stimulating the nerve cells of the large bowel. Gerard (1633) notes ‘it is a singular purging medicine’ with over a page on its uses. When used regularly the nerves to the large bowel may be destroyed, leaving a permanently dilated large bowel that never functions properly again. This is a plant which causes the condition it treats to become permanent. Additionally, with prolonged use, the lining of the bowel turns black, serum potassium levels may fall, resulting in cardiac irregularities and sometimes death. Coma, neuropathy and hepatitis have also been reported. It is advertised on television (the actor involved is seen to be depressed and bloated until she takes Senokot, after which she is happy - Hippocrates would have attributed this antidepressant effect to the plant's ability to purge her of the black melancholic humour present in her bowel motions). It is available without prescription or health warning against long-term use. What do you think? Lyte (1578) recommends it strongly for depression, but one might claim to be cured rather than take it again. Photographed in the Medicinal Garden of the Royal College of Physicians, London.