Tarwi

What does Tarwi look like?

Tarwi is an annual lupin, a legume like peas and beans. Its stem is hollow and much branched, and the plant stands anywhere from half a metre to 2.8 metres tall, taller in northern South America than in the southern Andes. A strong taproot reaches 3 metres down, and the roots carry nodules of nitrogen-fixing bacteria. Each leaf is palmate: one leaf divided into five to twelve oval or lance-shaped leaflets. The flower, or corolla, is 1 to 2 cm with five petals and may be white or purple. Pods run 5 to 12 cm and hold two or three bone-white seeds, sometimes up to nine.

Where does Tarwi come from?

The species comes from the Andean region of Ecuador, Peru and Bolivia, where it shows its greatest genetic variability. People there domesticated it more than 1,500 years ago, drawn by the protein in its seed. In Quechua it is tarwi, pronounced tarhui; Spanish speakers in the region call it chocho. Its bitter taste kept it little known beyond the Andes. Cultivated types with less bitterness came out of breeding work that began in Germany in the 1930s. Today the bean is being taken up more widely as a plant-based protein.

When and how Tarwi blooms

It suits cool climates and is grown mainly in high tropical valleys, from 800 to 3,000 metres up. It tolerates severe drought, and mature plants survive frost, though seedlings do not. Farmers sow seed directly, traditionally after minimum tillage, at about 100 to 120 kg per hectare. Improved practice adds phosphorus and potassium before sowing and uses 90 kg of selected seed spaced 60 to 80 cm apart. The seeds sprout quickly because of their high fat content. The growing cycle takes 150 to 360 days, depending on genotype, altitude and conditions.

How Tarwi is used

Andean people have eaten the seed since ancient times, in soups and stews, in salads, or on its own with boiled maize. It is more than 40% protein and about 20% fat, with a soft coat that cooks easily. The bitterness comes from quinolizidine alkaloids; soaking the seeds in water for several days removes them, but cooking alone does not. Milk made from the seeds is used for cheese and yogurt. The plant also fixes nitrogen, leaving 60 to 140 kg per hectare for the crop that follows.

Kinds of Tarwi

Colour varies widely, from white to purple, with white recessive to purple. Plants differ in shape too. The commonest type branches in a V, which gives the most biomass; the basal branching type sets its seed heads at one level. Northern South American plants grow taller than southern Andean ones, and the genome, with 2n = 48 chromosomes, is highly variable. Early varieties ripen in about 150 days, which lets them be rotated with potatoes and cereals.

What Tarwi means

Tarwi has fed Andean people since ancient times and stayed a local crop, partly because its beans are bitter until treated. In the high valleys it is valued both as food and as a soil improver, and its alkaloids can act against pests, including nematodes that trouble potatoes. Breeders now work on steadier yields, earlier and more even ripening, and tolerance of disease and insects. One aim is a plant with high alkaloids in its leaves but low levels in the seed.

Questions people ask about Tarwi

Good reading and sources

• USDA Plants DatabaseUS Department of Agriculture, Article
• Plants of the World OnlineRoyal Botanic Gardens, Kew, Plant database
• Where it has been recordedGBIF, Plant database
• Sightings and photos by naturalistsiNaturalist, Plant database

• Lupinus mutabilis on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data