Pollan uses the apple tree on the frontier, whose seeds were brought there in part courtesy of John Chapman, as a symbol of the human desire for sweetness. In the days before the widespread commercial availability of sugar, the apple was one of the sweetest substances around, and its seeds were used to make cider. Americans brought apple seeds with them on their westward journeys, changing the frontier, and the apple tree itself morphed in the New World to become heartier and more adapted to its new home.

The tulip is one of what Pollan refers to as the four “canonical flowers” (61), which also include the rose, the peony (particularly in Asia), and the orchid. These flowers are symbols of beauty, and the tulip was so prized in early 17th century Holland that it caused a feverish speculation in tulips referred to as “tulipomania” (93). Pollan tries to figure out why the tulip was regarded so highly, and he concludes in part that its form is a perfect mixture of Apollonian (symmetrical, rational) and Dionysian (wild, uncontrolled) forms and that it brought color to the monochromatic Dutch landscape.