Madigascar Periwinkle – Princess of Wales Conservatory, Kew Gardens, Richmond upon Thames, London, England

Madagascar periwinkle was for many years grown simply as an attractive bedding plant in tropical areas. It comes in a range of pinks and reds that give rise to its other common name, rosy periwinkle. But today it has a more serious purpose; planted around the world during colonial times, it quickly became known at the same time as a useful folk medicine for diabetics. American and Canadian researchers during World War Two became aware that soldiers stationed in the Philippines were using it instead of insulin during shortages.

As a consequence, after the war, lab testing was done in earnest on Madagascar periwinkle. This revealed that the plant contained thirty alkaloids, strong plant chemicals that might be of use to humans. The leaves were found to contain two particularly valuable alkaloids, vinblastine and vincristine. These alkaloids work by disrupting part of cell division or "mitosis," stopping the process when newly copied DNA is split into two identical parts to produce two identical new cells.

The drug company Eli Lilly tested the new chemicals on mice and found they helped to combat cancers, in particular those of the bone marrow such as childhood leukaemia and non-Hodgkin’s Lymphoma. They developed an effective chemotherapy treatment, and today the prognosis for sufferers has changed from a one in ten chance of survival, to at least an eight out of ten chance of some remission.