Sweet potatoes are an iconic Japanese treat, but they’re not native to Japan.

Originally from Central America, these tubers came through China in the 17th century to the Satsuma domain in southern Kyushu. Some say a fisherman named Riemon Maeda brought the first sweet potatoes to Satsuma after a trip to the Ryukyu Kingdom (present-day Okinawa), which explains why today’s Kagoshima Prefecture is dotted with memorials to this humble act.

Over time, sweet potatoes became a valued crop in the Satsuma domain, where conditions favored them over rice. During nationwide famines, Satsuma’s nutrient-dense sweet potato crop spared its people the worst of the suffering. So helpful was this foreign crop that in 1735, the eighth Tokugawa shogun ordered a court scholar to look into growing the food — now known as “satsumaimo” (literally, “Satsuma potato") — across Japan.