Japanese name: ナガイモ（長芋） Scientific name:Dioscorea polystachya
[Overview]
A climbing perennial.
The cylindrical underground stem becomes enlarged.
The stem has ridges and, like the petiole, is tinged with purple.
Leaves are simple and opposite (rarely in whorls of 3), heart-shaped to ovate, 6–9 cm long, with a pointed tip.
The base of the leaf extends out on both sides like ears.
The leaf veins are tinged with purple.
The leaf margin is entire.
Bulbils form in the leaf axils.
It is dioecious.
Male inflorescences stand erect from the leaf axils, and female inflorescences hang down.
Both male and female flowers are white, with 6 tepals.
The fruit is an obovate-round capsule 1.8–2 cm in both length and width, with 3 wings.
The seeds are flat and round, about 5 mm across, with a wing around them.
[Uses]
The tuber is made into dishes such as tororo-jiru (grated yam soup), and it is also used medicinally.
[Cultivation]
Propagate from seed tubers.
The roots extend deep into the soil, so deep tilling is necessary.
