nasturtium, any plant of the genus Tropaeolum, tropical American herbs (usually climbing) native to mountainous areas of South and Central America. Several species are cultivated in the United States as ornamentals for their yellow or red flowers, e.g., the common nasturtiums (T. majus and T. minus) and the canary-bird flower (T. peregrinum). These species have been hybridized. The plants are sometimes used for food, i.e., the tuberous rooted T. tuberosum or añu of the high Andes, the seeds (pickled as capers), and the tart flowers and leaves (used in salads). Properly, Nasturtium is the botanical name for the water cresses, an unrelated genus of the family Cruciferae (mustard family). Nasturtiums are classified in the division Magnoliophyta, class Magnoliopsida, order Geraniales, family Tropaeolaceae.

Any of various annual plants of the genus Tropaeolum (family Tropaeolaceae), native to Mexico, Central America, and northern South America, and cultivated elsewhere as garden plants. Brilliant yellow, orange, or red flowers are funnel-shaped and have a long spur that contains sweet nectar. The peppery-tasting leaves and flowers are sometimes used in salads, and the young flower buds and fruit are sometimes used as seasoning. Nasturtium also is a genus of aquatic herbs in the mustard family (see watercress).

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