This group includes the familiar garden nasturtium and Canary creeper, climbing like clematis by twisting theirstalks round any available support. T. majus is the common nasturtium, an growing to 2.1 m (7 ft) or more and flowering from June to September. Dwarf and trailing strains are available.
T. peregrinum, Canary creeper, is a perennial grown as anin this country. It is a rapid climber, up to 3m (10 ft) in a season, and produces its bright yellow from June to September. T. speciosum , or flame nasturtium, is a perennial growing to about 3.6m (12 ft), with flame-red flowers from July to September. It is the only one of the group that does not like full sun, and although it comes from Chile, it seems to prefer cold, damp conditions – a north-facing wall is ideal. T. tricolorum does not climb very high – only 90-120 cm (3-4 ft) – but is worth growing for its unusual three-colour flowers, purple, orange/ red, and yellow. T. tuberosum is a vigorous climber, up to 3m (10 ft), with red and orange flowers.
Some strains do not flower until September and are then cut down by frost. Look for the early flowering variety, which blooms in June. T. peltophorum is an annual with red flowers, similar to T. majus but less vigorous, growing to 1.8 m (6 ft).
General care: Canary creeper needs average garden soil but the othershould be given poor soil or they will produce a lot of vegetation at the expense of the flowers. Most of the perennials will thrive in any good fertile soil, but T. speciosum must have an acid soil. Add peat if necessary to achieve this. T. tuberosum and T. tricolorum grow from tubers which will survive the winter only in the mildest areas. If in doubt, lift and store in a frost-free shed, planting out again in May when all danger of frost has passed.
Propagation: Thecan be grown from sown in April into the flowering site, or sown in of soil-less in March for planting out later after hardening off. The tubers of T. tuberosum and T. tricolorum can be divided when they are lifted for over-winter storage. The other perennials can be propagated by dividing the in March.
Pests and diseases: Tropaeolum are attacked by blackfly, cabbage caterpillars and thrips: derris will deal with all these. Mottled or spottedare caused by viruses, for which there is no cure.