Tropaeolum speciosum aka Flame Nasturtium

Tropaeolum speciosum is considered a challenging plant to grow successfully. It is notoriously difficult to establish and has very specific requirements: acidic to neutral soil, cool moist summers, and the classic 'cold feet, warm face' positioning where roots stay shaded while foliage reaches into sunlight. Once established (which can take 5-10 years to reach full size), it becomes quite hardy and can even become vigorous in ideal conditions like Scotland's climate.

Tropaeolum speciosum requires consistently moist but well-drained soil. During establishment, it's critical never to let the plant dry out. Water regularly, especially during hot or dry periods, but ensure good drainage to prevent waterlogging. The plant thrives in cool, moist summers and may struggle in hot, dry conditions. In ideal climates with regular rainfall, additional watering may be minimal once established.

Tropaeolum speciosum requires acidic to neutral soil (pH below 7.5) that is rich in organic matter. A humus-rich, leafy soil that is moist but well-drained is ideal. The plant tolerates clay, loam, or sandy soils provided they have good organic content.

Tropaeolum speciosum follows the 'cold feet, warm face' principle: roots should be kept cool and shaded while the top growth climbs into full sun or partial shade. This is why it's ideal for growing through evergreen hedges or shrubs. Position on a north or northeast-facing aspect where roots remain cool, or provide shade at the base while allowing foliage to reach sunlight. Avoid positions with intense, direct sun at the base.

Tropaeolum speciosum is fully hardy in temperate climates, tolerating winter temperatures down to -15°C to -10°C (RHS H5 rating, USDA zones 8-10). It dies back completely in winter and re-emerges in spring. However, it prefers cool summers and may struggle in areas with hot, dry conditions. The tubers are sensitive to high temperatures, which can induce early dormancy. Scotland's mild, moist climate suits it particularly well.

Tropaeolum speciosum thrives in humid conditions with cool, moist air. It performs best in maritime climates with regular rainfall and moderate humidity, which is why it flourishes in Scotland and western coastal areas. In drier regions, regular watering and mulching can help compensate, but the plant may not reach its full potential without naturally humid conditions.

Tropaeolum speciosum benefits from being planted in humus-rich soil amended with plenty of organic matter such as leaf mould or well-rotted compost. During the growing season, a gentle organic fertilizer can be applied, but avoid high-nitrogen feeds which may promote foliage at the expense of flowers. Annual mulching with organic matter in spring helps maintain soil fertility and moisture levels.

Tropaeolum speciosum is notoriously difficult to propagate. Seed germination is unreliable: soak seeds for 24 hours, sow in compost with a grit topping, and maintain temperatures below 5°C for many weeks. Germination may take months or even years. Root cuttings or division of established rhizomes in early spring offer better success rates. For most gardeners, purchasing established plants is the most practical approach.

Tropaeolum speciosum is a climbing perennial that reaches 2.5-4 metres in height with a spread of 0.5-1 metre. It takes 5-10 years to reach full size, climbing through or over other plants using its slender stems. Once established, it spreads via underground rhizomes and forms deep-rooting tubers. The plant produces long fleshy rhizomes and rounded leaves composed of 5-7 leaflets.

Tropaeolum speciosum produces striking bright scarlet flowers from summer through autumn (typically July-October in the Northern Hemisphere). The tubular flowers are about 2cm wide with long spurs and frilly edges. After flowering, the plant develops ornamental indigo-blue berries held within red sepals, extending the display into late autumn. The intense red flowers are produced profusely when the climbing stems reach sunlight.

Tropaeolum speciosum is primarily an outdoor plant and performs poorly indoors. It is fully hardy to -15°C (USDA zones 8-10, RHS H5) and thrives in temperate climates with cool, moist summers. It grows particularly well in Scotland, western Britain, and similar maritime climates. Plant it to climb through evergreen hedges or shrubs, with roots in shade and foliage reaching into sunlight. In New Zealand and some temperate regions, it can become invasive.

Tropaeolum speciosum is native to southern and south-central Chile in South America, where it is known locally as coralito, quintralito, or voqui. It grows naturally in the temperate forests of the Chilean Lake District and Patagonia. The cool, moist climate of its native habitat explains why it thrives in similar conditions in Scotland and western Britain. It was first described scientifically in 1836 by Poeppig and Endlicher.

Tropaeolum speciosum requires minimal pruning. The plant dies back naturally each winter, with stems dying to ground level. In early spring, simply cut dead growth down to ground level to tidy the plant before new shoots emerge from the rhizomes. Vigorous established plants may spread more than desired; control by removing unwanted shoots or limiting rhizome spread with barriers.

Tropaeolum speciosum may be affected by glasshouse whitefly and spider mites, particularly in warmer or more sheltered conditions. It can also be susceptible to virus diseases. In its preferred cool, moist conditions, pest problems are generally minimal. Good air circulation and avoiding water stress help prevent issues. The plant is generally robust once successfully established.

In spring, cut back dead growth as new shoots emerge from rhizomes. During summer, maintain consistent moisture and monitor for pests; this is peak flowering season. In autumn, enjoy the blue berries and allow foliage to die back naturally. In winter, the plant is completely dormant underground. Apply mulch in autumn or early spring to protect rhizomes and maintain soil moisture and acidity. No winter protection is needed in zones 8-10.