Decton Hylton guided his tractor through a grove of pecan trees whose canopy of leaves filtered the sun. As we drove across the 1,638-acre farm near Albany, Georgia, on a scorching day last October, Hylton told me about the nut’s history in the South. In the nineteenth century, he said, an enslaved man known only as Antoine, who worked as a gardener on a Louisiana plantation, was one of the first people to experiment with grafting pecan trees. He was largely responsible for turning the nut into a commercial crop, and the variety he developed is called Centennial. “It’s…