Perum valli kizhangu, ratalu in Hindi and kachil in Malayalam, is the greater or purple yam, one of the most widely grown yams in the tropics. Its large tubers have white or deep purple flesh. Gujarat cooks ratalu into undhiyu, Kerala into kachil puzhukku, and the Philippines makes purple yam into ube desserts. Raw tubers contain irritant crystals and must be cooked.
- Botanical name
- Dioscorea alata L.
- Family
- Dioscoreaceae
- Tamil
- Perum valli
- Hindi
- Ratalu
- Parts used
- Cooked tuber
- Habit
- Greater yam vine with winged stems and large cooked tubers
- Last updated
- 2026-10-27
How to recognise Perum valli
It is a vigorous climbing vine with square stems that carry four thin wings along their length.
The leaves are heart-shaped, glossy and usually set opposite each other.
Small aerial bulbils sometimes form in the leaf axils.
The underground tuber is large, often several kilograms, with brown skin and white, cream or purple flesh.
Lesser yam has round, prickly stems and small, clustered tubers.
Traditional use of Perum valli
Kitchen
In Gujarat purple ratalu is cubed and slow-cooked with other winter vegetables in undhiyu.
Gujarati food practice
Kitchen
In Kerala kachil is boiled and mashed with coconut and spices into puzhukku.
Kerala food practice
Kitchen
In the Philippines purple yam, ube, is cooked with milk and sugar into halaya and used in desserts.
Filipino food practice
Modern notes on Perum valli
The tubers are mostly starch and supply fibre, potassium and vitamin C.
Purple types are rich in anthocyanins, which give them their colour.
Raw yam contains calcium oxalate crystals that irritate skin and mouth; cooking breaks them down.
Perum valli safety
Always cook yam thoroughly. Oil your hands or wear gloves when peeling raw yam.
Ecology and sourcing
It was domesticated in South-east Asia or New Guinea.
It rarely produces seed and is grown from tuber pieces.
It has escaped and become invasive in Florida.
Related plants
Also in Dioscoreaceae
Questions about Perum valli
What is ube?
Purple greater yam, used in Filipino desserts.
Why does raw yam itch?
It contains needle-like oxalate crystals.
How do I recognise the vine?
Its square stems have four thin wings.
Is ratalu sweet potato?
No. Sweet potato is Ipomoea batatas.
Can Perum valli be eaten raw?
No. Always cook it.
Sources
- Dioscorea alata L. — Plants of the World Online, Kew (search) (accessed 2026)
- Wikidata item Q1932852 (Dioscorea alata)
Educational page about a plant. It is not medical advice, not a diagnosis, and not an offer to sell. Traditional use is historical. If you need care, ask a licensed clinician. Questions: hello@meevamed.com.