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Mendocino Coast Botanical Gardens, 47 acres of botanical bliss fronting the Pacific Ocean

Nasturtiums

Edible flowers and foliage make this a joy in the garden

Botanical Name: Tropaeolum majus Common Name: Nasturtium Family: Tropaeolaceae 

Description: The garden nasturtium, also known as Indian cress, belongs to the order Geraniales, the genus Tropaeolum, and the species, majus. There are approximately eighty species in the Tropaeolum family. The only other one commonly used for ornamental gardening is the canary bird flower, Tropaeolum peregrinum, which is a climber that can reach 15 ft. and has bright yellow flowers with curiously fringed upper petals.

The garden nasturtium is an herbaceous ornamental that includes both trailing and non-trailing varieties and can be annual or perennial depending on the variety and climate. A warm climate favors the development of perennials, whereas frost limits the plant to an annual. Tropaeolum majus originated in the Andes Mountains of Peru. It has since spread throughout the Americas and Europe but, excepting intentional garden plantings, it is mainly confined to mild coastal conditions. It grows naturally in all the coastal counties of California through Mendocino.

At Greenwood Beach in Elk, Mendocino County, a large community can be seen on the on the left as you hike down to the beach, twining on the hillside and up through the shore pines. The particular variety there has leaves up to seven inches across and dislikes direct sun, mainly preferring shade with some late afternoon sun. A demarcation occurs on the bank where full sun begins, and no nasturtiums grow past that point in this particular microclimate.

The overall impression of a bed of nasturtiums, or a wild occurrence of the climbing perennial, is aesthetically pleasing, its round leaves spiderwebbed by veins from the junction of the central petiole like the elongated triangles of a pizza, its bright flowers waving in a light wind between the impressive, deep green, symmetrically round leaves (whose lobes are hardly visible from a short distance). The flowers of the nasturtium range from yellow to orange to red, each plant primarily of one color and often streaked with others.

Each flower is composed of 5 petals, with 2 upper and 3 lower, a 5-lobed calyx with a long spur and 8 stamens of varying size. The blooms can exceed 2.5 inches. In a frost-free climate they can bloom all year. The plant's seeds are composed of a 3-segment fruit from which one large seed in each cluster usually goes on to maturity, sometimes more, when it dries up into crinkly brown pods about 1/3" in diameter.

Cultivation: The more shade nasturtiums have, the larger the leaves become but the blooms are less. With too much sun or too little water the leaves and stems become bleached, stringy, with a yellowish cast. On Greenwood Beach itself, near the north end, there is a pine in which trailing nasturtiums climb to its very top, using it as a shelter from both wind and sun. Where not protected they reflect the sickly color and stringy appearance described above, though they bloom more prodigiously, as if in a greater hurry to propagate, given the less than ideal conditions. The garden nasturtium prefers well-drained, light (sandy) and medium (loamy) soils, and can grow in nutritionally poor soil. The plant can thrive in acid, neutral and basic (alkaline) soils. It requires moist soil. If the soil is too rich, lush foliage will grow at the expense of flowers. Although some authorities say the nasturtium cannot grow in shade, by my observation it requires only minimal sun to flourish. In gardens nasturtiums are useful as a crop to be planted next to cabbages and other vegetables, as it attract aphids away as well as white butterflies ("cabbage moths"), who prefer nasturtiums to most vegetables.

Cultivars: Various cultivars of garden nasturtiums are available through seeds. Tropaeolum majus nanum is non-trailing, yields variegated foliage conspicuously marked with creamy white flowers in a good range of reds, oranges and yellows. Tropaeolum majus 'Empress of India' is over 100 years old, a non-trailing annual with deep crimson-scarlet flowers on compact plants with dark bluish green foliage. It is a hardy and has been extant as a variety for over 100 years. Tropaeolum majus 'Tall Single Blend' is a prolific hardy annual climber to 6 feet, with large flowers in a blend of brilliant reds, oranges and yellows.

Propagation and Harvest: Nasturtiums can be propagated by seeds, cuttings, and by their vine-like runners. The plants are self-seeding so annuals will return in a colder climate the following spring, usually in April. In milder climates the roots can regenerate the plant if the plant is only superficially removed. For these and other reasons some consider the nasturtium invasive, even though its roots are shallow. Nearly all the parts of the nasturtium are edible. The leaves and especially the flowers have an unusual, fragrant peppery taste, described as "hot watercress," and can be added with good advantage to salads. The green seeds can be pickled as a substitute for capers, and the dry seeds can be ground for a pepper substitute. Nasturtium flowers and leaves are extremely high in Vitamin C. The large seeds, easy to handle, along with the rapid growth of the plants, flowering within weeks, make for an ideal introduction to horticulture for young children. The author was introduced to them by a teacher at the age of five, the first plant he grew from a seed.

Submitted by Master Gardener Craig Chaffin, 2007.