Tropaeolum tuberosum aka Mashua

Tropaeolum tuberosum is a tuber-forming vine in the nasturtium family, Tropaeolaceae. Its names include mashua, añu, and Peruvian nasturtium. It comes from western South America, where people have long grown it for food. Its range spans Colombia, Ecuador, Peru, Bolivia, and northwest Argentina. Wild plants grow on mountain slopes and in valleys. They also grow in damp scrub and wooded sites high in the Andes.

This herbaceous perennial sends up new stems from its tubers each year. It climbs or trails across the ground and nearby plants. Its leaf stalks twist around supports to hold the stems. Plants reach about 6.6 feet (2 metres) tall and wide. One account gives a greater height of 9.8 feet (3 metres). The leaves are large and dark green. Small yellow flowers add colour, and bees visit for nectar and pollen. Each flower has both male and female organs, and plants are self-fertile.

Give it sun above ground and shade around the roots. It needs moist soil that drains well. Sandy soil or loam suits it, with a mildly acid to neutral pH. Hot, dry summers can cause it to become dormant. PFAF lists flowers from June to October, but day length affects bloom and tuber growth. Most forms need short days, so a mild autumn helps the crop mature. Cold tolerance varies between accounts: dormant tubers may withstand about 28°F (-2°C). PFAF reports survival near 23°F (-5°C) with mulch. Frost can damage new shoots. In cold areas, lift dormant tubers and store them somewhere cool and frost-free.

Gardeners grow mashua as both a food crop and an ornamental. Its trailing growth can cover soil and help limit erosion. The leaves can shade nearby crops. Sources report strong resistance to insects and disease. They also describe compounds that act against bacteria, insects, and nematodes. PFAF does not flag the plant as weedy.

The tubers, leaves, and flowers are edible. Cook the peppery tubers; some people find their taste too strong. Freezing them after cooking can improve the flavour. Eat the leaves raw or cooked, and use the flowers as food. Tubers supply vitamin C, and dried tubers contain up to 16% protein. Both plant databases report no known hazards. PFAF also records traditional use to reduce sexual desire and reports effects on male hormones.