Dioscorea polystachya or Chinese yam is a vine with a thick, edible tuber.
Sounds tropical, right? Nope, this is a very hardy plant that tolerates down to -20 °C easily.
It is a vigorous grower that forms each year stems of 3-5 m long and fastly cover any climbing support.
The tuber as well as the bulbils (also called air potatoes) can be eaten. They taste somewhat like potatoes and can be prepared in the same way: by cooking, frying, baking…
Harvesting and storage is also to potatoes: harvesting in late summer to early fall, winter storing in a cool, dry place. Although you can leave the tuber in the ground and dig it out in the winter to eat it.
The hardest with this plant is digging the tuber up as it can be up to 1 m long, so that’s a big job.
It is best planted in open ground in the garden. It could be grown in pot but the first year, because the tuber is then much smaller, about 0.5 kg. It gets bigger with age.
It is also known by the name Dioscorea batatas but the currently accepted name is D. polystachya.
Dioscorea polystachya is a climber with a thick, spindle-shaped underground tuber. The tuber grows vertically and can be up to 1 m and weigh more than 2 kg.
The stems twine counterclockwise and are up to 3-5 meters long. They produce bulbils (small tubers also known as air potatoes) in the leaf axils, which are about 2 cm in diameter.
The leaves are alternate, 3-9 cm long and 3-11 cm wide. The petiole is the same length as the leaf blade. The lower leaves are usually oval to heart-shaped, upper leaves sagittate with 3 lobes.
The plant is dioecious. Female flowers occur in the leaf axils, in a spike of 3-5 spikes of up to 5 cm long, in zigzag form. The male flowers occur in the leaf axils, up to 5 cm long. The flowers are very small. The flowers smell like cinnamon.
The fruit is a capsule, globose, 1.7 to 2 cm long and 1.5-3 cm wide. The seeds are winged
Dioscorea polystachya is quite invasive but easy to control:
- harvest the tuber during the first years of growth
- harvest the bulbils before they ripen and fall to the ground
- if you have male and female plants near each other, remove the fruits before they ripen to avoid distribution by wind
- alimentary: both the tuber and bulbils are edible
- medicinal: traditional medecine
Chinese yam, cinnamon vine, cinnamon yam, common yam, Shan Yao, wild yam
Dioscorea batatas f. clavata, Dioscorea batatas f. daikok, Dioscorea batatas f. flabellata, Dioscorea batatas f. rakuda, Dioscorea batatas f. tsukune, Dioscorea cayennensis var. pseudobatatas, Dioscorea decaisneana, Dioscorea doryphora, Dioscorea potaninii, Dioscorea pseudobatatas, Dioscorea rosthornii, Dioscorea swinhoei
Dioscorea: after Pedianus Dioscorides, a Greek physician, pharmacologist and botanist (around 40-90 AD)
Polystachya: from the Greek poly (many) and stachys (grain ear)
Temperate Asia: China, Japan, Korea
Forests, scrub, grasslands, mountain slopes, along rivers and roadsides, between 100-2500 m altitude
USDA zone 5-11
Nutritious and well drained
Sun (preferably), partial shade
The bulbils are best harvested in late summer to early fall, before they are fully ripe and fall to the ground.
The tuber can be harvested throughout the year but it is easier to harvest it in late summer to early autumn. He can be left in the ground, growth resumes next spring.
Store in a cool and dry place during the winter.
- cut a piece of about 15 cm from the tip of the tuber. This is best done when you are going to eat the tuber.
- the tuber can be stored in a dry and cool place during winter
- plant root cuttings in spring
- harvest the bulbils before they are ripe and fall to the ground in late summer or early fall
- overwinter in dry conditions
- plants in the spring
- the first year, the underground tuber will be about 0.5 kg. The following years the tuber gets much bigger.
- sow in March or April in a warm place, indoors or in a heated greenhouse
- cover the seeds with a thin layer of topsoil
- 20 °C
- germination time: 1-3 weeks