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Species in cultivation

The most common flower in cultivation is a hybrid of T. majus, T. minus, and T. peltophorum. It is commonly known as the nasturtium (and occasionally anglicized as nasturtian). It is mostly grown from seed as a half-hardy annual, and both single and double varieties are available. It comes in various forms and colours, including cream, yellow, orange and red, solid in colour or striped and often with a dark blotch at the base of the petals. It is vigorous and easily grown and does well in sun. It thrives in poor soil and dry conditions, whereas rich soil produces much leafy growth and few flowers. Some varieties adopt a bush form while others scramble over and through other plants and are useful for planting in awkward spots or for covering fences and trellises.

The following cultivars have gained the Royal Horticultural Society 's Award of Garden Merit:

The blue nasturtium (Tropaeolum azureum) is a tender species from Chile which has violet-blue flowers with white eyes that can be as much as 4 cm (1 + 1 ⁄ 2 in) across.

Tropaeolum brachyceras has 2.5 cm (1 in) yellow flowers with purplish markings on wiry, climbing stems. It is a half-hardy perennial from Chile and may remain dormant for several years before being sparked into growth by some unknown trigger factor.

Tropaeolum hookerianum is a tuberous-rooted species from Chile. There are two subspecies, T. h. austropurpureum which has violet-purple flowers and T. h. pilosum with yellow flowers.

The Canary creeper (Tropaeolum peregrinum) is a trailing and climbing half-hardy annual species with wiry stalks and palmately lobed leaves. The pale yellow, fringed flowers are borne on long stalks. It originated from Peru but may first have been cultivated in the Canary Islands before being introduced into Western Europe.

Wreath nasturtium (Tropaeolum polyphyllum) is a prostrate plant originating from Argentina and Chile. It has silvery, deeply lobed leaves and a profusion of small, bright yellow flowers on long trailing stalks. After flowering, the plant dies back. It is a perennial with underground rhizomes which send up new shoots at intervals. It will survive for several years in a suitable sunny location with well-drained soil. It is a very hardy species; the tubers can grow at depths of 60 cm (24 in) enabling the plant to survive at altitudes of as much as 3,300 metres (10,000 ft) in the Andes.

The flame flower (Tropaeolum speciosum) is well adapted to cool, moist climates and famously does well in Scotland. It sends up shoots that thread their way through hedges and shrubs and, when they emerge into the light, bear brilliant red flowers among small, five or six-lobed leaves. It is difficult to establish but is an attractive garden plant when it thrives. This plant has gained the Royal Horticultural Society's Award of Garden Merit.

Three-coloured Indian cress (Tropaeolum tricolor) is another tuberous, climbing species grown for its attractive red, purple and yellow tubular flowers. It comes from Chile and Bolivia and is a reliable winter-growing species.

Mashua (Tropaeolum tuberosum) is a perennial climbing plant from the Andes grown for its tuberous roots. It has been cultivated since ancient times, and depictions of it are found at archaeological sites pre-dating the Incas. It has leaves with five to seven lobes and small, long-spurred, red and yellow flowers. The tubers have an unpleasant smell when raw, which disappears on cooking. It is frost-hardy and produces crops of 30 tonnes per hectare at an elevation of 3,000 metres (9,800 ft) above sea level. The cultivar T. tuberosum lineamaculatum 'Ken Aslet' has gained the Royal Horticultural Society's Award of Garden Merit.

Species originating from the coastal areas and lower foothills make most of their growth in winter, whereas the true alpine species are summer growers. Tuberous Tropaeolum species are well known for occasionally remaining dormant for one or more years. The species with underground rhizomes and tubers can be propagated from these, while other species are best raised from seed. Many growers favour fresh seed, but dried seed is also often successful. Seed from the winter growing species should be sown in the autumn, while the summer growing species are best sown in the spring in well-drained compost and covered with 1 to 2 cm (1 ⁄ 2 to 3 ⁄ 4 in) of grit or sand. The containers should be kept at below 4 °C (39 °F) until the seedlings appear in about a month, as too high a temperature inhibits germination.