Walking the grounds of Sanssouci Palace in Potsdam, you might stumble across a peculiar gravestone that is covered with potatoes. Perhaps even more confusingly, the stone bears the name of King Fredrick the Great of Prussia. While this may seem odd, it is actually a sign of respect and gratitude to Der Kartoffelkönig (“the potato king”). Though potatoes are a large part of diets around the world, this was not always the case. The potato plant, which is native to South America, didn’t even find its way to Europe until well…