Japanese name: ナガイモ（いちょういも群）（長芋） Scientific name:Dioscorea polystachya
[Overview]
A dioecious climbing perennial.
Most plants are female.
Taxonomically the Tsukune-imo group is the same species, and they are distinguished by the shape of the tuber and other features.
The stem has ridges and, like the leaf stalks, is tinged with purple.
The leaves are usually opposite and heart-shaped to ovate.
Bulbils form in the leaf axils.
In Kanto it is called "yamato-imo," and the tuber is flat, shaped like an Icho leaf.
[Uses]
The tuber has little harshness and is very sticky, so it is used for tororo (grated yam) and similar dishes.
[Cultivation]
Propagation is by seed tubers.
It grows deep into the soil, so the soil must be tilled to nearly 1 m.
