Nasturtium is a flowering herb originating in highland areas of South America, its natural range extending along the Andes mountains from Colombia to Bolivia.
The stems are soft, succulent and grow quickly with a trailing habit, branching and spreading out along the ground as well as cascading over walls and climbing up on structures such as fences, to heights of up to 2 m (6.6 ft). In warm climates, without frost or extreme heat and with adequate moisture it is perennial and is self-propagating, putting down roots as well as re-seeding as it grows.
The leaves are medium-green, disc-shaped with wavy margins, in diameters from 5 to 15 cm (2 to 6 in). They are held above the ground on long, erect leaf stalks and with the leaf edges overlapping, shading the ground beneath them.
It blooms throughout the year, producing solitary, trumpet-shaped flowers on erect stalks, in shades of yellow, orange or red, contrasting starkly with the green of the leaves. They are succeeded by roundish, pea-sized green fruit divided into three spongy segments, each enclosing a single seed.
In the tropics, the leaves and flowers tend to be most abundant during the cooler months of the year.
It is widely cultivated in gardens for its ability to cover ground quickly, suppress weeds and conserve soil moisture, its interesting foliage and brightly coloured flowers a bonus. In addition, the flowers attract hummingbirds, butterflies, bees and other beneficial insects to the garden, making it highly suitable for companion planting, especially in vegetable beds. It is also well-suited, on account of its trailing and cascading habit, to poolside landscapes, containers and raised garden beds.
Both the young leaves and flowers are edible and have a sharp, peppery taste that has been likened to watercress, and which comes from the presence of mustard oil. They are used as a garnish and are added to salads for their taste, colour and visual interest. The older leaves are not normally used as they are strongly flavoured and somewhat bitter. The unopened flower buds are pickled whole, usually in a flavoured brine and compare closely to capers in how they are prepared and eaten.
Grows naturally in humid cool subtropical and tropical mid- to high-elevation climates, generally best in frost-free areas with annual lows of 9 to 18 °C, annual highs of 20 to 27 °C, annual rainfall of 700 to 3500 mm and a dry season of 5 months or less.
Nasturtiums can also be cultivated with irrigation in much drier and warmer climates, though with markedly less success due to the plant's inability to cope with excessive dry and heat.
New plants can be grown either from seed or cuttings and perform best on moderately fertile, free-draining loam and sand soils of a slightly acid to slightly alkaline nature, generally with a pH of 6.0 to 7.5. Rich soils, with high levels of nitrogen, encourages leaf growth, often at the expense of flowering.
Over-exposure to the hot afternoon sun can cause it to die back and become unsightly. For this reason, it is best grown in tropical lowland areas as an annual, in the cool months of the year and with shade from the afternoon sun. In cool, high elevation areas it grows well in full sun all year round.
The fruit are buoyant and easily dispersed by moving water, which enables the seed to be carried a far distance. It is listed as a serious weed in at least one reference publication and is assessed to be a high weed risk species for Hawaii by the Hawaii Pacific Weed Risk Assessment project (HPWRA).
Adams, C. D. 1972, Flowering plants of Jamaica, University of the West Indies, Mona, Greater Kingston
Editors of Sunset Magazine 2012, The New Western Garden Book: The Ultimate Gardening Guide, 9th edition, Sunset Publishing Corporation, California
Griffiths, M. & Burras, J. K. 1994, Manual of climbers and wall plants, Royal Horticultural Society (Great Britain), Timber Press, Portland, Oregon
Iremonger, S. 2002, A guide to plants in the Blue Mountains of Jamaica, University of the West Indies Press, Kingston, Jamaica
Jamieson, G. S. 1943, Vegetable fats and oils : their chemistry, production, and utilization for edible, medicinal and technical purposes, 2d ed, Reinhold, New York
Jex-Blake, A. J. 1957, Gardening in East Africa : a practical handbook, 4th ed., Royal Kenya Horticultural Society, Longmans, Green and Company, London
Macmillan, H. F. 1943, Tropical planting and gardening : with special reference to Ceylon, 5th ed, Macmillan Publishing, London
Martin, F. W & Ruberté, R. M. 1975, Edible leaves of the tropics, U.S. Agency for International Development (USAID), and the Agricultural Research Service, U.S. Department of Agriculture (USDA), Mayaguez, Puerto Rico
Randall, R. P. 2007, The introduced flora of Australia and its weed status, Cooperative Research Centre for Australian Weed Management, Glen Osmond, South Australia
Rubatzky, V. E. & Yamaguchi, M. 1997, World vegetables : principles, production, and nutritive values, 2nd ed., Chapman & Hall, New York
Weiss, E. A 2002, Spice crops, CABI Publishing, Wallingford, United Kingdom
Woodward, Penny 1997, Pest-repellent plants, Hyland House, South Melbourne
This website is provided for general information only. Iplantz makes no statements, representations or warranties as to the accuracy or completeness of the content of this website and does not accept any liability to you or any other person for the information which is provided or referred to on this website.
In particular, Iplantz does not represent or warrant that any dataset or the data it contains is accurate, authentic or complete, or suitable for your needs. Changes in circumstances after the time of publication may impact the accuracy of datasets and their contents.
To the maximum extent permitted by law, Iplantz accepts no liability whatsoever to any person arising from or connected with the use of or reliance on any information or advice provided on this website or incorporated into it by reference, including any dataset or data it contains. No responsibility is taken for any information or services that may appear on any linked websites.