Properties
The hardy yam (Dioscorea batatas / Dioscorea polystachya), also called Chinese yam or cinnamon vine, is a perennial root crop superior to potatoes in many ways that can weight several kilograms.
Most people think of yams as being tropical plants that can’t be grown in temperate climates, but there are a few species that will thrive in colder climates, hardy yam being one of them. This species comes from the mountains of northern Japan and can tolerate temperatures down to about -20°c.
Plants take 3 – 4 years to reach full maturity, though one year roots of well grown plants can weigh more than 500g. The main problem with this plant is harvesting it, you have to dig deep!
Here’s what the roots look like when grown in deep rich soils in raised beds. Often use removable planks on sides of beds for easy harvest of delicate tubers. From an Asian market in New Haven Connecticut. Photo: Eric Toensmeier
Where It Grows
It is native to China, Japan, and Korea, and is naturalized in the central and eastern United States. It’s hardy to USDA zone 4-5 and UK zone 5. It likes a deep, well-drained and moist soil.
The yam can be invasive if left unchecked. It invades and takes over open to shady areas in the Eastern United States and likely similar climate zones.
Young vine (2 years) showing yields of bulbils. Photo: Eric Toensmeier
Why We Like It
- The edible root of this yam can grow to 500 grams in the first year, and 2 kg or more in the second year if grown in a good deep soil.
- The root has a very nice flavor with a floury texture when baked, it is not as tasty as a sweet potato but is better than most yams and superior to potatoes.
- The tubers can be boiled, baked, fried, mashed, grated and added to soups.
- They store well and for a long time and can also be left in the ground and harvested as required in the winter, making it very suitable for use as a staple food.
- The aerial tubers which are produced in abundance are reported to be edible and very tasty.
- Because yams produce a very vertical root, it is possible to grow a number of plants very close to each other, perhaps at 20 – 30cm spacing.
- Very high yields are possible, quite a bit higher than potatoes and with none of the disease problems associated with potatoes.
- This is a very easily grown plant that succeeds in most fertile well-drained soils. It prefers a position in full sun, though it will also succeed in semi-shade.
- Yam tubers are used medicinally in China and Japan. It’s called Shan Yao in Chinese herbalism and is seen as a sweet soothing herb that stimulates the stomach and spleen and has a tonic effect on the lungs and kidneys.
- From Plants for a Future: “The tuber contains allantoin, a cell-proliferant that speeds the healing process. It is used internally in the treatment of poor appetite, chronic diarrhoea, asthma, dry coughs, frequent or uncontrollable urination, diabetes and emotional instability. It is applied externally to ulcers, boils and abscesses. The tubers are harvested in the autumn and can be used raw or baked.”
The “berries” / air tubers of the hardy yam. Photo: Eric Toensmeier
