Tropaeolum majus, the garden nasturtium, nasturtium, Indian cress or monks cress, is a species of flowering plant in the family Tropaeolaceae, originating in the Andes from Bolivia north to Colombia. An easily-grown annual or short-lived perennial with disc-shaped leaves and brilliant orange or red flowers, it is of cultivated, probably hybrid origin. It is not closely related to the genus Nasturtium (which includes watercress).
The species was originally called Nasturtium indicum ("Indian nasturtium") but the plant is not related to the true Nasturtium genus.
The current genus name Tropaeolum, coined by Linnaeus, means "little trophy". Tropaeolum is the diminutive form of the Latin tropaeum, itself borrowed from Ancient Greek τρόπαιον : trópaion "trophy".
It is a fast-growing plant, with trailing stems growing to 0.9–1.8 m (3–6 ft). The leaves are large, nearly circular, 3 to 15 cm (1 to 6 in) in diameter, green to glaucous green above, paler below; they are peltate, with the 5–30 cm long petiole near the middle of the leaf, with several veins radiating to the smoothly rounded or slightly lobed margin.
Nasturtium leaves, like some other species, demonstrate the lotus effect, whereby rainwater falling on the surface gathers into globular droplets which roll off the leaf, leaving it dry and clean. Electron microscope scanning reveals tiny bundles of waxy particles which repel the water.
The flowers are 2.5–6 cm in diameter, with five petals, eight stamens, and a 2.5–3 cm long nectar spur at the rear; they vary from yellow to orange to red, frilled and often darker at the base of the petals. The fruit is 2 cm broad, three-segmented, each segment with a single large seed 1–1.5 cm long.
Das Elisabeth Linné-Phänomen, or the Elizabeth Linnæus Phenomenon, is the name given to the phenomenon of "flashing flowers". Especially at dusk, the orange flowers may appear to emit small "flashes". Once believed to be an electrical phenomenon, it is today thought to be an optical reaction in the human eye caused by the contrast between the orange flowers and the surrounding green. The phenomenon is named after Elisabeth Christina von Linné, one of Carl Linnaeus's daughters, who discovered it at age 19.
The garden nasturtium is used as a food plant by the larvae of some Lepidoptera species including the dot moth and the garden carpet moth. A common pest found on nasturtiums is the caterpillar of the large white or cabbage white butterfly.
The species has become naturalized in parts of the United States (California, New York, Pennsylvania, New Hampshire, Massachusetts, Connecticut and Virginia), as well as parts of Europe, such as Gibraltar, and Asia, Africa and Australia. It is listed as invasive in Hawaii and Lord Howe Island, Australia.
Tropaeolum majus cultivars are widely grown as easy annual plants, for poor, damp soil in full sun. The large seeds are easy to handle individually.
As they do not tolerate heavy frost they are best sown under glass in heat, and planted out after all danger of frost has passed. Alternatively, as they are fast-growing, they may be sown in situ in May or June.
Many flower colours are available, in the warm spectrum from cream through yellow, orange, red and maroon. Some have highly decorative marbling on the leaves.
All of the above-ground parts of the plants 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 flowers contain about 130 mg vitamin C per 100 g (3+1⁄2 oz), about the same amount as is contained in parsley. Moreover, they contain up to 45 mg of lutein per 100 g, which is the highest amount found in any edible plant. The unripe seed pods can be harvested and dropped into spiced vinegar to produce a condiment and garnish, sometimes used in place of capers.
Some color varieties
Flowering yellow and red
Flower showing nectar spur
Underside of leaf showing petiole attachment
Flower cut through to show structure
Lobed leaf morphology
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