Solanum curtilobum

Solanum curtilobum, or rucki, is a potato from the Andes. It is a perennial: it lives for more than two years. It belongs to Solanaceae, the nightshade family. Kew gives its native range as Peru to Bolivia. Other sources list northern Argentina as well. Growers raise it for food in high Andean fields. These sites often lie above 12,470 feet [3,800 metres]. Plants For A Future lists no known wild habitat.

This herb grows from a rootstock that forms tubers. Its stems reach about 1.6–3 feet [0.5–0.9 metres]. Useful Tropical Plants also gives a height of 2.5 feet [0.75 metres]. It calls the plant a hybrid, a cross between two potatoes. One parent is Solanum juzepczukii. The other is tetraploid Solanum tuberosum, with four chromosome sets. Rucki has five such sets and can form fertile seed. Its flowers have both male and female organs.

Rucki provides food where cold puts crops at risk. Yields are low, but its ability to bear frost gives it value. Both gardening sources rank it among the hardiest potatoes. It grows where frost may strike on 300 days each year. Yet Plants For A Future also calls it frost tender. These claims conflict, so no firm hardiness rating is possible. Useful Tropical Plants says people grow it in temperate regions too. It also lists crops in subtropical regions.

Choose sun or light shade and moist, rich soil. Add organic matter, but avoid wet ground or heavy clay. It grows in several soil types but likes slightly acid soil best. Limy soil or too little humus can lead to tuber scab. Plants For A Future says to plant tubers in spring. Harvest them in autumn once frost kills the top growth. Keep planting tubers cool and free from frost through winter. Start seed in a warm greenhouse in early spring. Move the young plants outdoors after the last expected frost.

The small tubers yield starch but taste bitter. Sources list cooked tubers as the part to eat. Freeze-drying takes out the bitter taste to make chuño. Plants For A Future lists no medicinal or other uses. Its safety warning concerns the wider genus, not findings on this species. It cites no direct report that rucki is toxic. This gap does not mean other plant parts are safe to eat.