An apple fruit is a disposable womb of the mother tree, but the seeds it encloses are new individuals, each containing a unique combination of genes from the mother tree and the mystery dad, whose contribution arrived in a pollen packet inadvertently carried by a springtime bee. If that seed grows into a tree, its apples will not resemble its parents’. Often they will be sour little green things, because qualities like bigness, redness, and sweetness require very unusual alignments of genes that may not recur by chance. Such seedling trees line the dirt roads and cellar holes of rural America. If you like the apples made by a particular tree, and you want to make more trees just like it, you have to clone it: Snip off a shoot from the original tree, graft it onto a living rootstock, and let it grow. This is how apple varieties come into existence. Every McIntosh is a graft of the original tree that John McIntosh discovered on his Ontario farm in 1811, or a graft of a graft. Every Granny Smith stems from the chance seedling spotted by Maria Ann Smith in her Australian compost pile in the mid-1800s. The fine points of apple sex were lost on most US colonists, who planted millions of apple seeds as they settled farms and traveled west. Leading the way was John Chapman, a.k.a. Johnny Appleseed, who single-handedly planted hundreds of thousands of seeds in the many frontier nurseries he started in anticipation of the approaching settlers, who were required to plant 50 apple or pear trees as part of their land grants. Even if they had understood grafting, the settlers probably wouldn’t have cared: Although some of the frontier apples were grown for fresh eating, more fed the hogs or the fermentation barrel, neither of which was too choosy. Every now and then, however, one of those seedling trees produced something special. As the art of grafting spread, those special trees were cloned and named, often for the discoverer. By the 1800s, America possessed more varieties of apples than any other country in the world, each adapted to the local climate and needs.