The rhizomes. Photo from
This member of the Dioscoreaceae
family was given this name by Tomitarô Makino in 1891. It is found
in China, Japan, Korea and Russia, growing in a rich soil with some to lots
of water and little to some sun. The rhizomes can grow up to five
centimetres in diameter and 50 centimetres long, The vines can reach
five or even ten meters. Besides from being eaten, the rhizomes are
used to extract steroids.
I do not know, if they
can have their rhizomes exposed, or how old each rhizome will grow.