Tropaeolum /trɵˈpiːələm/, commonly known as nasturtium (/næˈstɜrʃ(i)əm/; literally “nose-twister” or “nose-tweaker”), is a genus of roughly 80 species of annual and perennial herbaceous flowering plants. It was named by Carl Linnaeus and is the only genus in the family Tropaeolaceae. The nasturtiums received their common name because they produce an oil that is similar to that of watercress(Nasturtium officinale).
The genus Tropaeolum, native to South and Central America, includes several very popular garden plants, the most commonly grown being T. majus, T. peregrinum and T. speciosum. The hardiest species is T. polyphyllum from Chile, the perennial roots of which can survive underground when air temperatures drop as low as −15°C (5°F).
Plants in this genus have showy, often intensely bright flowers, and rounded, peltate (shield-shaped) leaves with the petiole in the centre. The flowers have five petals (sometimes more), a three-carpelled ovary, and a funnel-shaped nectar tube at the back.