Water Yam, Purple yam, Greater yam, White yam
Dioscorea alata

Family: Dioscoreaceae

What it is like

Water Yam or Dioscorea alata is a tuberous root vegetable originated in the Asian tropics. Its tubers are usually bright lavender in colour. It is also known as purple yam, greater yam, Guyana arrowroot, ten months yam, white yam, and winged yam. It is perennial, fast growing, and climbing plant that grows up to 15 m long. The tubers are cooked ? used in variety of desserts and as flavouring. It can be toxic if eaten raw. Medicinally, it is used as a laxative and verfimuge and used to treat fever, gonorrhoea, leprosy, tumours, and inflamed haemorrhoids.

Dioscorea alata is an evergreen Perennial Climber growing to 15 m (49ft) by 0.5 m (1ft 8in) at a fast rate. See above for USDA hardiness. It is hardy to UK zone 10. The flowers are pollinated by Wind, Insects. The plant is not self-fertile. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils, prefers well-drained soil and can grow in nutritionally poor soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in semi-shade (light woodland). It prefers moist soil.

Height (m): 15

Where it is found

Not known in a wild state.

Probably arose in cultivation in E. Asia - Malaysia.

Conservation Status: This taxon has not yet been assessed.

Countries/locations it is found in

Africa, Anguilla, Asia, Australia, Barbados, Benin, Brazil, Burma, Cambodia, Cameroon, Caribbean, Central Africa, Central America, China, Colombia, Comoros, Congo DR, Cook Islands, Costa Rica, Côte d'Ivoire, Cuba, East Africa, East Timor, Ethiopia, Fiji, Gabon, Gambia, Ghana, Guiana, Guinea, Guinée, Guinea-Bissau, Guyana, Haiti, Hawaii, Honduras, India, Indochina, Indonesia, Ivory Coast, Jamaica, Japan, Laos, Madagascar, Malawi, Malaysia, Mali, Marianas, Mexico, Mozambique, Myanmar, Nauru, New Caledonia, New Zealand, Nigeria, North America, Northeastern India, Pacific, Palau, Papua New Guinea, Philippines, Polynesia, Puerto Rico, Samoa, SE Asia, Senegal, Sierra Leone, Solomon Islands, Southern Africa, South America, Sri Lanka, St Lucia,

How it is used

Food

Rating: 4

Root - cooked. Usually boiled or baked and used as a vegetable. An average of 3 roots are produced by the plants, these usually each weigh in the range of 5 - 10kg, though exceptionally they can weigh up to 60 kg. The root needs to be properly cooked, it can be toxic if eaten raw. The plant produces aerial tubers and these can be eaten in the same way as the tubers.

Root: includes bulbs, corms, tubers, rhizomes etc.

Colouring: edible dyes

Medicine

Rating: 1

The tuber is grated, mixed with brown stout vinegar, then spread onto paper and placed on the small of a woman's back to prevent or forestall a threatened miscarriage. Although available as a dietary supplement and used in folk medicine, there is no clinical evidence that D. alata has any therapeutic properties. D. alata supplements may have adverse effects in people taking estrogens, anticoagulant drugs or during pregnancy and breast-feeding. D. alata has relatively high levels of oxalates (486–781 mg/100 g dry matter).

Other

Rating: 2

Fodder/animal feed. Agroforestry. Ornamental. Medicinal: Traditional/folklore. Purple variety colour is due to various water-soluble anthocyanin pigments and is used as a food colouring agent.

Dye: Plants that provide dyes.

Fodder: Food given to the animals (including plants cut and carried to them) rather than forage for themselves.

Food Forest: Plants for Edible Forest Gardens and Food Forests.

How it is grown

Plants grow best in lowland tropical areas up to an elevation of 1,000 metres with a temperature around 26 - 34°c; a well-defined dry season of 4 - 5 months; and a total rainfall of 1,000 - 1,500mm evenly distributed throughout the remainder of the year. Plants are not frost tolerant. Amongst the many cultivars of this species, there are forms that are tolerant of a wide range of environmental conditions. For best yields, this species requires a deep, well-drained, sandy loam that is not liable to water-logging. It also grows well in medium to clay loams. Although more tolerant of poor soils than most other members of this genus, plants respond well to the application of organic matter. Prefers a pH in the range 5.5 - 6.5, tolerating 4.8 - 8.5. Daylengths of more than 12 hours are preferred during the early growing season since this encourages vegetative growth; daylengths of less than 12 hours towards the end of the growing season will encourage tuber formation and development. Plants take 7 - 10 months to mature a crop. Yields of 20 - 25 tonnes per hectare have been obtained. There are some named varieties. A dioecious species, both male and female plants need to be grown if seed is required.

Propagating it: Seed - rarely produced in cultivation, they are not normally used to propagate this species. Cuttings of tubers. Small tubers can be cut into 2 - 4 sections, larger ones into 6 - 8 sections. Each section should have 2 - 3 dormant buds. The cut tuber is often left in the sun for several hours to promote wound healing and reduce the risk of fungal infection. Aerial tubers can also be used, they usually produce vigorous plants.

Best place to grow:

Habit: Perennial Climber

Hardiness: 10-12

Growth: Fast

Soil: Light (sandy), medium, heavy (clay)

Shade: Semi-shade

Moisture: Moist

Things to keep in mind

Edible species of Dioscorea have opposite leaves whilst poisonous species have alternate leaves. The uncooked tuber of this species is toxic, and is said to produce narcosis. Saponin is present and cooking renders the tubers safe to eat.

Vigorous twining herbaceous vine invasive outside cultivated areas. It is included in the Global Compendium of Weeds (Randall, 2012), and is listed as a “noxious weed” in Florida and as an invasive species in Cuba, Costa Rica and several islands in the Pacific.

Its other names

Local names

geflügelter yam, grande igname, greater yam, guyana arrowroot, igname ailée, igname de chine, inhame, sewalli kodi, storjams, tabena, ten-months yam, wasser yamswurzel, water yam, white yam, winged yam, yam, ñame blanco, ñame de agua, Ambi, Asiatic yam, Avase, Ba-chhim, Batatilla, Boboyassi, Chupri alu, Cucam, Cucui-mo, Dago, Damloong chhiem moen, Dandaba, Daunini, Duok, Ep, Gbara-gue, Goradu, Huwi, Igname ailea, Ilumbelumbe, Kaavathu, Kachchilkilangu, Kachil, Kaile, Kamo, Kap, Katalu, Katula, Kep, Kham, Khamalu, Khanulu, Khoai-mo, Kinampai, Kiseba, Kwalo kau, Lengu, Lipeta, Luktu, Mach alu, Man-sao, Man, Manbuo, Mon, Nane, Nangate, Nruireu, Obbi, Oewi, Onthalaigasu, Oo-yama-imo, Oobi, Ovy, Pacala, Pahui, Pandalamu, Perumvalli kizhangu, Pindalu, Pokok ubi, Ractaguranialu, Raja-ala, Rambachim, Ratula, Sakourou, Shen shu, Taai-shue, Tarul, Telngot, Tung-genasu, Tus, Ubi tiyang,

Synonyms

Dioscorea atropurpurea Roxb. Dioscorea globosa Roxb. Dioscorea javanica Queva. Dioscorea purpurea Ro