Plant 389

Tropaeolum species (Tropaeolaceae)


By 1597, English herbalist John Gerard (1545-1612) was growing the sprawling Tropaeolum minus, with its bright yellow-orange flowers, in his Holborn garden. He had received seeds from Jean Robin (1550-1629), gardener to the French kings. However, the species’ origin was South America, from where it had been introduced by the Spanish in the 1560s. Approximately fifty years later, this species was being grown in Oxford Botanic Garden. Today, the most familiar of the nasturtiums is the climber Tropaeolum majus and its cultivars, which may have originated in gardens through complex inter-specific hybridisations.

For Gerard, Tropaeolum minus was a novelty, although ‘the smell and taste doth shewe it to be a kind of Cresses’. At this time, the plant’s origin and its odour gave it both its English common name ‘Indian cress’ and its ‘learned’ name ‘Nasturtium Indicum’ (literally ‘Indian nose-torturer’). However, it was the leaves reminiscent of shields, the trophies of warfare, that inspired the modern generic name Tropaeolum, from the Greek tropaion meaning ‘trophy’. The odour and taste of Tropaeolum is due to the presence of mustard oils, the same compounds that give cabbage, mustard and cress their distinctive flavours.

The genus Tropaeolum, with approximately 100 species, is the sole member of the family Tropaeolaceae, which is native to Central and South America. In addition to the leaves, the bilaterally symmetrical flowers of Tropaeolum have a distinctive combination of five showy petals, eight stamens and a backwardly pointed, funnel-shaped nectar spur formed by modification of one of the sepals. Outside their native ranges, members of the genus are known as vividly coloured horticultural plants, which often produce their best displays on poor soils. Tropaeolum species are also edible. For example, preserved in vinegar or salt, the leaves and buds of Tropaeolum minus and Tropaeolum majus are substitutes for capers, whilst their flowers are used as garnishes.

In the Andes, yellow-orange-flowered mashua (Tropaeolum tuberosum), identified as one of the ‘lost crops of the Incas’, is one of the four most important tuberous food plants in the region. It is particularly well adapted to subsistence agriculture at elevations of greater than 3,000 metres, on marginal soils, where it can be very productive. The distinctive, strong, spicy flavour of the tuber diminishes with cooking and processing, although it has a reputation as an anti-aphrodisiac. In the sixteenth century, there are even reports that Incan soldiers were fed it for this precise purpose.

Christenhusz, MJM 2012. 745. Tropaeolum minus. Curtis’s Botanical Magazine 29: 324-330.

Christenhusz, MJM 2012. 746. Tropaeolum majus. Curtis’s Botanical Magazine 29: 331-340.

Grau A et al. 2003. Mashua (Tropaeolum tuberosum Ruíz & Pav.). IPGRI.

Stephen Harris