Chinese Yam
Dioscorea polystachya
Chinese Yam (Dioscorea polystachya), also known as Cinnamon Yam or Nagaimo, is a climbing tuberous vine in the Dioscoreaceae cultivated for its large, cylindrical underground tubers. Unique among yams, the Chinese Yam tuber can be eaten raw — its crisp, slippery, slightly sweet flesh is a prized ingredient in Japanese and Chinese cuisine.
• Also called "Nagaimo" (long yam) in Japanese, "Shanyao" in Chinese, and "Ma" in Korean
• One of the few yam species whose tubers can be consumed raw without cooking
• When grated raw, the tuber becomes a slimy, glutinous paste (tororo) valued in Japanese cuisine
• The tubers can grow remarkably large — specimens exceeding 1 meter in length have been recorded
• Also produces aerial bulbils (small potato-like growths) in leaf axils that are edible
• A staple food in East Asia for thousands of years
Taxonomy
• Grown as a food and medicinal plant in China for over 2,000 years
• Widely cultivated in China, Japan, Korea, and Taiwan
• Introduced to Europe and North America as an ornamental and food plant
• Has become invasive in parts of the eastern United States, where it is sometimes called "cinnamon vine"
• The genus Dioscorea contains approximately 600 to 800 species, distributed across tropical and temperate regions
• The name "yam" derives from the West African word "nyami" (to eat), via Portuguese and Spanish
• The genus was named by Linnaeus in honor of the ancient Greek physician Pedanius Dioscorides
Vine:
• Slender, twining (clockwise), 2 to 5 meters long
• Green to purplish, smooth or sparsely hairy
• Dies back to the ground each winter in temperate climates
Leaves:
• Alternate (sometimes opposite), broadly ovate to hastate (arrow-shaped), 5 to 15 cm long
• Often with basal lobes projecting outward
• Dark green, with 7 to 9 prominent veins
• Long petioles with winged bases
Aerial bulbils:
• Small, knobby, irregular tuber-like growths, 1 to 3 cm, produced in leaf axils
• Dark brown exterior, white interior
• Capable of sprouting into new plants when they fall to the ground
Underground tuber:
• Large, cylindrical, often unbranched, 30 to 100+ cm long and 3 to 8 cm in diameter
• Brown, rough, thin skin
• White, crisp, slightly mucilaginous flesh
• May grow very deep (30 to 100 cm below surface)
Flowers:
• Small, greenish-yellow
• Male and female flowers on separate plants
• Borne in axillary spikes or panicles
Per 100 g raw tuber:
• Energy: approximately 118 kcal
• Carbohydrates: 24 g (including significant amounts of mucilaginous polysaccharides)
• Protein: 2.0 g
• Fat: 0.1 g
• Vitamin C: 5 to 10 mg
• Potassium: 350 to 500 mg
• Vitamin B6: significant
• Contains allantoin — a compound that promotes cell proliferation and wound healing
• Rich in dioscorine and other glycoproteins
• Contains significant amounts of digestive enzymes including amylase and diastase
• The mucilaginous polysaccharides support digestive health
• Low glycemic index compared to potatoes
Planting:
• Plant tuber pieces or small whole tubers in spring, 8 to 15 cm deep
• Requires deep, loose, fertile, well-drained soil — tubers can extend 1 meter deep
• Plant near a trellis, fence, or support for the climbing vines
• Space 30 to 45 cm apart in rows 90 to 120 cm apart
Site:
• Prefers full sun to partial shade
• Rich, loamy, deep soil is essential for long, straight tubers
• Consistent moisture throughout the growing season
Care:
• Provide climbing support — vines are vigorous
• Mulch heavily to conserve moisture
• Water during dry periods
Harvest:
• Harvest tubers in late autumn after foliage dies back
• Dig carefully — tubers are long, deep, and brittle
• Can be left in the ground over winter and harvested as needed in milder climates
• Aerial bulbils can also be collected and eaten or saved for planting
• Raw: grated into tororo (slimy, glutinous paste) — a Japanese delicacy served over rice, soba noodles, or tuna
• Sliced raw in salads — crisp and refreshing
• Added to miso soup and nabemono (hot pot)
• Lightly cooked in stir-fries — retains some crispness
• Deep-fried as tempura
• Boiled, steamed, or mashed like potato
• Dried and ground into yam flour
• In Chinese cuisine, stir-fried with vegetables or added to soups
• In Korean cuisine, grated and mixed with other ingredients in bindaetteok (pancakes)
Medicinal uses:
• Important in Traditional Chinese Medicine as "Shan Yao" — used for spleen and stomach health
• The allantoin content promotes healing of ulcers and wounds
Fun Fact
Chinese Yam is one of the few root vegetables in the world that is traditionally eaten raw — when grated, its crisp flesh transforms into a slippery, mucilaginous paste that Japanese diners pour over rice like a savory sauce, a texture that is considered a delicacy in East Asia but can be surprising to Western palates.
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