For nearly 150 years, starting in the late 17th century, millions of people living in Ireland subsisted largely off one crop: the potato. Then, in 1845, farmers noticed that their potato plants’ leaves were covered in mysterious dark splotches. When they pulled potatoes from the ground, most were shrunken, mushy and inedible. The blight spread alarmingly quickly, cutting yields from that year’s harvest in half. By 1846, harvest from potato farms had dropped to one quarter of its original size.
