About 80 species, see text.
Nasturtium (pronounced /næˈstɜrʃⁱəm/) literally "nose-twister" or "nose-tweaker"), as a common name, refers to a genus of roughly 80 species of annual and perennial herbaceous flowering plants in the genus Tropaeolum (pronounced /trɵˈpiː.ələm/, "trophy"), one of three genera in the family Tropaeolaceae. It should not be confused with the Watercresses of the genus Nasturtium, of the Mustard family. 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).
They have showy, often intensely bright flowers (the intense color may pose problems in macrophotography), 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.
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.
Cultivation and uses
In cultivation, most varieties of nasturtiums prefer to be grown in direct or indirect sunlight, with a few preferring partial shade.
The most common use of the nasturtium plant in cultivation is as an ornamental flower. It grows easily and prolifically, and is a self-seeding annual.
All parts of the plant are edible. The flower has most often been consumed, making for an especially ornamental salad ingredient; it has a slightly peppery taste reminiscent of watercress, and is also used in stir fry. The unripe seed pods can be harvested and pickled with hot vinegar, to produce a condiment and garnish, sometimes used in place of capers, although the taste is strongly peppery. The mashua (T. tuberosum) produces an edible underground tuber that is a major food source in parts of the Andes.
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