How Sweet Potatoes Saved Japan

In The Daydreamer Detective, Mei returns home to her mother's farm, broke and jobless, just in time to help with the fall harvest. Her mom puts her to work picking sweet potatoes, and Mei grudgingly admits that they are her least-hated vegetable. That small detail has a rich history behind it — because sweet potatoes have a very special place in the hearts of Japanese people, and very nearly saved Japan from total starvation in the 18th century.

A History of Famine

Back in the days of the samurai, Japan routinely went through famines caused by poor weather or pest infestations. Governments and lords did their best to find alternative crops to rice — the staple that everyone depended on — to feed the population when the harvest failed.

In 1732, crop failures and pests led to another devastating famine, later called the Great Kyōhō Famine. A call went out for anyone who could provide a solution. A scholar named Aoki Konyō — lovingly called "Professor Sweet Potato" — believed that farming sweet potatoes on a large scale was the answer. At the time, sweet potatoes were only cultivated in southern areas of Japan, near Okinawa, and couldn't be brought north because they spoiled too quickly.

Konyō worked tirelessly to develop a strain of sweet potato that could survive in the cooler climates of central and northern Japan. Resistant to bad weather, high-yield (one vine can produce six or more potatoes), able to grow in poor soil, and plantable season after season — his first successful crop was in 1735. From that point on, sweet potatoes helped save countless lives across Japan.

After World War II

During and after World War II, rice was strictly rationed. Sweet potatoes were planted everywhere people could find space — school gardens, home gardens, public parks. They were so vital that they even appeared on the black market. People took trains out to the countryside just to buy them, because city transport couldn't bring food in fast enough.

Satsuma-imo

In Japan, the sweet potato is called satsuma-imo. "Imo" (pronounced EE-mo) refers to all fleshy tubers — potatoes, sweet potatoes, yams, taro. The "satsuma" comes from the Satsuma Prefecture (now Kagoshima), a port that regularly received ships from other nations — including ships that brought the sweet potato into Japan.

Today, the Japanese love sweet potatoes in all forms: roasted whole, boiled in a sweet soy sauce stock, made into tempura, or steamed and eaten on a cold winter day. You can buy roasted sweet potatoes from street vendors throughout Japan — the cry of the sweet potato seller's cart is a beloved sound of autumn.

So next time you eat a sweet potato, remember how special they are to Japan — and how even Mei, the reluctant farmer, can't help but appreciate them.