Water Yam
Dioscorea alata
Water Yam (Dioscorea alata), also known as Winged Yam or Greater Yam, is the most widely cultivated yam species globally, producing enormous tubers that can exceed 40 kg. Named for the distinctive winged stems that distinguish it from other yam species, Water Yam is a critical staple food across tropical Africa, Southeast Asia, the Pacific, and the Caribbean.
• The species epithet "alata" means "winged," referring to the distinctive flattened, winged stems
• The most widely distributed cultivated yam species in the world
• Tubers can be enormous — specimens exceeding 40 kg have been recorded
• Called "ube" or "ubi" in the Philippines, where purple varieties are used to make the famous purple yam desserts
• The purple-fleshed varieties are one of the most visually stunning foods in existence
• A true yam (Dioscoreaceae), completely unrelated to sweet potatoes (which are often mislabeled as "yams" in American supermarkets)
Taxonomy
• Domesticated approximately 5,000 to 8,000 years ago in Island Southeast Asia
• Spread westward to India and eastward through the Pacific Islands in prehistoric times
• Reached West Africa through Portuguese trade routes in the 1500s, where it became a major food crop
• Now grown throughout the tropics worldwide
• In the Philippines, purple ube has been a staple food and dessert ingredient for centuries
• The genus Dioscorea contains approximately 600 to 800 species, of which about 10 are cultivated
• The word "yam" derives from the West African "nyami" (to eat)
Vine:
• Climbing, twining (counterclockwise), 3 to 10 meters long
• Distinctively winged stems — square or rectangular in cross-section with thin, leafy extensions (wings) along the angles
• Green to purplish, smooth or sparsely hairy
Leaves:
• Large, ovate to hastate (arrow-shaped), 10 to 20 cm long
• Opposite (distinguishing it from most other yam species which have alternate leaves)
• Dark green, with 7 to 9 prominent veins
Tubers:
• Large, variable in shape (cylindrical, lobed, or irregular)
• Often produced in clusters of 2 to 5 per plant
• Skin: brown, rough, thin
• Flesh: white, cream, or vivid purple
• Size: typically 1 to 5 kg, but can exceed 40 kg
• Texture: starchy, moist, slightly sweet when cooked
Aerial bulbils:
• Produced in leaf axils — small (1 to 3 cm), knobby, dark brown
• Used for vegetative propagation
Flowers:
• Small, greenish-white to pale yellow
• Male and female flowers on separate plants
• Borne in axillary spikes or panicles
Per 100 g boiled yam:
• Energy: approximately 110 kcal
• Carbohydrates: 27 g (including significant starch and some fiber)
• Protein: 1.5 to 2 g
• Fat: 0.1 g
• Vitamin C: 5 to 10 mg
• Potassium: 300 to 500 mg
• Vitamin B6: significant amounts
• Manganese: good source
• Contains dioscorine and other storage proteins
• The purple varieties contain anthocyanins — powerful antioxidants
• Good source of complex carbohydrates with moderate glycemic index
Planting:
• Plant tuber pieces or small whole tubers in spring, 10 to 15 cm deep
• Space 50 to 100 cm apart in rows 1 to 1.5 meters apart
• Provide a trellis or support for climbing vines
Site:
• Full sun
• Well-drained, fertile, deep, loose soil
• Consistent moisture during the growing season
• Tropical temperatures (25 to 35°C)
Care:
• Mulch heavily to retain moisture
• Train vines onto supports
• Water during dry periods
Harvest:
• Harvest tubers 8 to 12 months after planting, when foliage begins to yellow and die back
• Dig carefully — tubers are large, deep, and brittle
• Handle gently to avoid bruising
• Cure in a warm, well-ventilated area for 1 to 2 weeks
• Store at 13 to 16°C — do not refrigerate
• Boiled, steamed, or baked as a starchy staple — similar to potato
• Mashed or pounded into fufu — a West African staple
• In Filipino cuisine: ube halaya (purple yam jam), ube ice cream, ube cakes, and ube pandesal
• Fried as yam chips or fries
• In curries and stews across tropical Asia
• Grated and fried as fritters
• Dried and ground into yam flour
• In Pacific Island cuisine: boiled or baked in earth ovens
The purple ube of the Philippines has become a global food trend:
• Ube ice cream, ube donuts, ube lattes, ube pancakes
• The vivid purple color makes ube desserts Instagram-famous worldwide
Fun Fact
In the Philippines, the purple Water Yam known as "ube" is not just a food — it is a cultural icon. The vivid purple color of ube desserts is so iconic that "ube" has become a color name in its own right, and the plant appears on the official seal of the Philippines' national research institute for root crops.
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