Yamaimo or yamanoimo yam grows wild in the mountains, its roots running very deep, requiring long and patient hours of digging before the vegetable can be prized out of the earth. The most-prized variety, a wild yam called jinenjo is particularly difficult to uproot. You need to dig a human-sized hole to get the entire thing out of the ground. I’ve watched it done.
The hard work continues in the kitchen. Yamaimo needs careful preparation. In order not to let it turn brown when grating, the key is to peel it thickly, and soak it in vinegar water for half an hour. Thereafter, one must pound it into a thick and sticky glue-like consistency.
Is it worth the effort? Adherents certainly think so. Mainly yam is used in this grated form, known as tororo. It’s a popular addition to soba buckwheat noodles, in tororo soba, and in a grated yam soup, tororo-jiru and as tororo-gohan simply served on white rice. If you happen to be passing through Shizuoka city, why not drop by the restaurant Motogumi Chojiya who have been serving tororo-jiru for 400 years! Tororo has a somewhat gloopy consistency that might take a little getting used to. It’s worth persevering.
Yam can also be deep-fried, added to wheat noodles to make yamakake udon, or sliced in long, rectangular strips and eaten with shoyu and wasabi dressing, topped with nori, as yamaimo no tanzaku. The latter is an izakaya staple rumored to have a ‘beneficial’ effect on the male libido, and providing energy during the strength-sapping midsummer heat. It’s a simple but very tasty dish.
Yam varieties include the less sticky, crunchy nagaimo, the club-shaped ichoimo (called Yamato-imo in and around Tokyo), and the gnarled root-like tsukune-imo (called Yamato-imo in Kansai). Confusing, isn’t it?
Yam is said to be especially good at combating natsubate, the tiredness that sets in during Japan’s long, hot summer and is also very good for the digestion.