Tōhoku region
Tōhoku was traditionally considered the granary of Japan because it supplied Sendai and the Tokyo-Yokohama market with rice and other farming commodities. Tōhoku provided 20 percent of the nation's rice crop. The climate, however, is harsher than in other parts of Honshū due to the stronger effect of the Siberian High, and permits only one crop a year on paddy fields.
Apios americana
The only place in the world today where American groundnut are commercially farmed in any significant quantities is in Japan. Before American groundnut was introduced to Japan, the people on the main island of Honshu and the northern island of Hokkaido were already familiar with a native, wild plant there called hodoimo (Apios fortunei) that was occasionally eaten as an emergency food. It is believed that sometime during the Meiji period (1868-1912) American groundnut was accidentally or deliberately brought to Japan. One theory is that American groundnut was accidentally brought to Japan as a stowaway weed among apple seedlings imported from North America. Another theory is that American groundnut may have been deliberately brought to Japan in the middle of the Meiji period as an ornamental flower. It is now considered a culinary specialty of the Aomori prefecture where American groundnut agriculture is centered and where it has been eaten for more than one hundred years. Although American groundnut agriculture is primarily identified with agriculture in the Aomori prefecture, it is grown in the nearby prefectures of Akita and Miyagi as well. In addition, it is known to be grown in the southern part of Honshu in the Tottori prefecture, and radioactive testing records following the Fukushima nuclear disaster record cesium testing of American groundnut agricultural products in the central prefecture of Tochigi. An important part of the spread and popularization of American groundnut consumption in Japan has been the efforts of Dr. Kiyochika Hoshikawa to promote the cultivation of this crop in Japan and the flurry of scientific articles on the health benefits of eating American groundnut tubers. Japanese websites that sell American groundnut continue to emphasize its health benefits in their marketing efforts. There are reports of American groundnut cultivation in South Korea as well where it is grown for its nutritional benefits