Nasturtium (literally "nose-twister"), as a common name, is a genus of roughly 80 species of annual and perennial herbaceous flowering plants Tropaeolum, one of three genera in the family Tropaeolaceae. This genus, native to South America 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).

They have showy, often intensely bright flowers (the intense color can make macrophotography quite difficult), and rounded, peltate (shield-shaped) leaves with the petiole in the center. The flowers have five petals (sometimes more), a three-carpelled ovary, and a funnel-shaped nectar tube in the back. The flowers can be added to salads for an exotic look and taste; they have a slightly peppery taste reminiscent of Watercress. The unripe seeds, when pickled, have been used as a substitute for capers. The mashua (T. tuberosum) produces an edible underground tuber that is a major food source in parts of the Andes.

Tropaeolum species are used as food plants by the larvae of some Lepidoptera species including Dot Moth and Garden Carpet. A very common "pest" found on Nasturtium in particular is the caterpillar of the Large White (Cabbage White) Butterfly.

The Nasturtiums receive their name from the fact that they produce an oil that is similar to that produced by Watercress (Nasturtium officinale), from the family Brassicaceae.

It is said that these flowers grow best in sun or light shade depending upon the variety.