Tropaeolum L. Tropaeolaceae cv Nasturtium. Distribution: South and Central America. As garden plants they are called nasturtiums, but the genus Nasturtium refers to plants, similar to watercress, in the Brassica family. The word 'nasturtium' whatever its usage comes from the Latin for a twisted nose, referring to the bitter taste that makes people's noses wrinkle. Tropaeolum comes from the Greek for a trophy, as Linnaeus thought the flowers climbing up columns resembled the Greek war trophies with golden helmets hanging on pillars (Stearn, 1994). The commonest horticultural species is T. majus
the flowers and leaves are edible, both raw and cooked, with a sharp, slightly bitter taste. This is due to a group of chemicals it shares with horseradish, wasabi, Brussels sprouts etc. called isothiocyanates, which are pest inhibitors in the living plants. T. tuberosum from the Andes is a root vegetable, cultivated and eaten like potatoes, also contains this chemical which means it can prosper without artificial insecticides, acaricides etc. Isothiocyanates have potential interest as adjuvants in anti-cancer treatments. Even more unusual is the reputation of T. majus for being an anaphrodisiac, a property that needs researching with the same enthusiasm as Marker and his colleagues showed when promoting the oestrogens and progestogens (synthesised from Mexican yams) as contraceptives. Photographed in the Medicinal Garden of the Royal College of Physicians, London.
