Rhubarb originated in western China, where it was prized as a medicinal ingredient. According to Zoroastrian lore, the first human couple emerged from the rhubarb plant. It made its way to Europe through Russia. In 17th-century England, it was used only medicinally, and was more expensive than opium. Europeans didn’t start eating rhubarb until 1778. In the U.S., it was first grown in Maine just before 1800. It’s a hardy plant that thrives in cold climates, and is a relative of buckwheat.