Writers and movie makers love to show medieval people eating hearty stews full of meat and potatoes. However, potatoes were not native to Europe, but to South America. In fact, even when they were first brought back by Spanish explorers in the 1500s, they remained nothing but a botanical curiosity for decades after. This small, lumpy tuber didn't become a dietary staple until the late 1700s. Why did the potato's acceptance take so long, despite its nutritive value?
One explanation is that the potato, Bittersweet, and Nightshade are all members of the same family. Medieval and Renaissance era herbalists would have immediately recognized its resemblance to these other poisonous plants, and assumed that it was poisonous as well.