The garden nasturtium is often associated with the “Elizabeth Linnaeus Phenomenon”, an optical illusion that makes the contrasting orange flowers and green foliage appear to flash brightly as it shakes in the wind. Garden nasturtium is cultivated as an ornamental plant. The disc-shaped leaves and seed pods are edible, usually getting used as garnishes and dressings.
I. Appearance and Characteristics
The garden nasturtium is often associated with the “Elizabeth Linnaeus Phenomenon”, an optical illusion that makes the contrasting orange flowers and green foliage appear to flash brightly as it shakes in the wind.
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”.
The Latin specific epithet majus means “larger” (the neuter form of major).
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.
Lotus effect
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.
Flowers and fruit
The flowers are 2.5–6 cm in diameter, mildly scented, 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.
The Elizabeth Linnaeus phenomenon
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.
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.
The garden nasturtium is used as a food plant by the larvae of some Lepidoptera species including the dot moth, the garden carpet moth and the large white or cabbage white butterfly.
II. How to Grow and Care
Sunlight
Nasturtiums grow and bloom best in full sun, receiving six to eight hours of direct sunlight per day. Although it can survive in partial shade, this plant might not produce as many flowers. However, given that hot temperatures can induce leaf browning, some shade is really preferable in warm climates.
Temperature
The garden nasturtium can’t survive a winter freeze, but it is somewhat drought tolerant and will survive heat waves to a certain extent. Its optimum growing temperature is between 55–70°F. The garden nasturtium is a medium drinker but needs good drainage and regular watering. It rarely tolerates damp soil, as excess water invites root rot.
Watering
Nasturtiums prefer weekly watering, but can be watered more frequently if grown in a greenhouse or a sunny vegetable plot. Nasturtiums can withstand moderate droughts, but their blooms will likely fade, and their foliage will become spindly.
Soil
Surprisingly, nasturtium flowers thrive in relatively infertile soil with adequate drainage. Overly rich soil produces a lot of greenery but few flowers. This plant grows best in soil with a neutral pH (6 to 8) and can tolerate dry conditions, though it prefers moderate moisture.
Fertilizing
Garden nasturtium flourishes with fertilization that supports blooming. For best results, utilize high phosphorus fertilizers to promote vibrant flowers. Fertilize garden nasturtium monthly during growing season; a light dose as per product instructions suffices. Excessive feeding can lead to more foliage than flowers. In cooler seasons, ease on fertilization as garden nasturtium’s growth slows. Always water garden nasturtium post-fertilization to prevent root burn and distribute nutrients. Novice and veterans should ensure granular fertilizers are evenly spread and liquid versions diluted accurately. Recall, a well-fed garden nasturtium is a visual delight.
Pruning
Pruning or deadheading the garden nasturtium is not necessary unless the plant is under stress and dead flowers are still hanging on to the stems.
Propagation
The garden nasturtium thrives when propagated via sowing in Spring, with moderate ease. Look for germination within 7-10 days as a sign of successful propagation. Ensure well-draining soil and adequate spacing for optimal growth.
Transplanting
The best time to transplant garden nasturtium is from late spring to mid-summer, ensuring optimal growth and blooming. Choose a sunny location with well-draining soil for successful transplanting. Remember to handle garden nasturtium gently, as its roots are delicate and can be easily damaged.
III. Uses and Benefits
- Ornamental uses
Popular in rock, cottage, vegetable, and herb gardens, the garden nasturtium is an old-fashioned plant that is widely cherished for its low maintenance, long bloom period, and unique fragrance. Gardeners may plant it in beds, borders, as ground cover, or even climbing plants to cover fences with a flowering vine. Owners may consider accompanying the garden nasturtium with flowers such as the signet marigold, sneezeweed, and English lavender.
- Medicinal uses
Some native South Americans used the plant medicinally, apparently due to its antibiotic and antibacterial properties. Some Europeans ate it to treat urinary and genital infections.
- Culinary uses
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.