no 14 (29.8.2020)
Ipomoea is the largest genus in the flowering plant family Convolvulaceae, with over 500 species, including both Morning Glory and, rather surprisingly, the vegetable Sweet Potato. The most usual Morning Glory in British gardens is the pretty ‘Heavenly Blue’ but we grow this one here because it looks more like the variety from which Dr Darwin’s medicine called Jalap would have been obtained.
Jalap was a drug made from the tuberous, turnip-like root of Convolvulus jalapa as Linnaeus called it, also known as Ipomoea jalapa or Ipomoea purga. The plant, a climbing, evergreen vine, reaching to about twelve feet, has heart-shaped leaves and trumpet-like purple flowers. It originated in South America and derived its name from the city of Xalapa, capital of the state of Veracruz in Mexico, which was also the home of Jalapeno chillies.
Mexican or Veracruz Jalap was introduced to Europe in the 16th century by Spanish explorers who referred to ‘purga de Jalapa’ meaning ‘purge of Jalapa’ which gives us a clue to its uses. Those who are familiar with Dr. Darwin’s favoured initial approach to all medical problems will understand why Jalap had to be included in his medicine list.
The ‘Family Herbal’ by Sir John Hill (d.1775) tells us that ‘the root is the part used, and druggists [apothecaries] sell it. Given in powder with a little ginger, to prevent its griping, it is an excellent purge…’ Dr Meyrick, his Birmingham contemporary, adds: ‘There is a tincture made from this root with brandy, and kept in the shops, which has all the effects of the root in substance, and may be thought by some to be more agreeable to take’. I should think they probably made the right choice.