The text, usually categorized as a Nature and Gardening book, presents the argument that four plants have shaped human evolution at least to the same extent that humans have shaped those plants' evolution. The text uses the standard biological term "co-evolution" to describe this synergistic process. The four plants considered are the Apple, consisting of Malus domestica and M. seiversii; the Tulip, consisting of about 100 species in the genus Tulipa; Marijuana, consisting of the species Cannabis sativa and C. indica, as well as hybrids; and the Potato, or Solanum tuberosum. The text does not consider, or even apparently realize, the problematical approach of discussing co-evolution of species at generally the genus level. The bulk of the narrative consists of anecdotal experiences, personal observation, opinion and summarized topical history—which does not particularly support the major thesis.

The book is presented in four chapters, each considering a particular plant. Chapter 1 presents the apple tree, with a heavy focus on its edible fruit. The chapter generally considers the species Malus domestica but includes M. seiversii, said to be the primitive ancestor, in some discussions. A basic recounting of the natural history of the apple is presented in summary form, along with concise notes about the apple's historic importance in human civilization. The introduction of the apple to America is particularly well-developed, with a nearly complete focus on the activities of John Chapman, better known as Johnny Appleseed. The apple is said to have exerted a decisive impact on human evolution because it is able to satisfy Homo sapiens' desire for sweetness.

Chapter 2 presents the tulip, with a heavy focus on its flower. The chapter considers the entire genus Tulipa and does not mention any of the roughly 100 species comprising it. The text considers the evolution of tulips and the co-evolution of humans and tulips but unfortunately does not elucidate the complexities of evolutionary theory at the level of the genus—a major failing. A rudimentary explanation of tulip natural history is presented. This is supplemented with a recounting of the establishment of the tulip as a garden flower in Europe with a special emphasis given to Holland, especially during the period of so-called tulipomania in the early 1600s. A more concise account then focuses on the tulip in Turkey during the early 1700s. The tulip is said to have exerted a decisive impact on human evolution because it is able to satisfy H. sapiens' desire for beauty.

Chapter 3 presents marijuana. The chapter considers the species Cannabis sativa and C. indica, as well as hybrids. Additional materials consider other psychoactive drugs and the entire class is presented as an evolutionary unit. Thus, the text considers the evolution of marijuana and the co-evolution of humans and marijuana but unfortunately does not elucidate the complexities of evolutionary theory considered for multiple species and hybrids. A fairly-convoluted natural history of marijuana is offered with a heavy focus on American developments. The chapter is the longest in the text but most of the material presented is a subjective consideration of the effects of using marijuana as a drug; much of the writing is rambling and many undeveloped topics are jumbled together. Modern growing techniques are briefly described and the larger sociological implication of psychoactive drug use is considered. The presentation is sympathetic to drug use and highly critical of American criminalization of marijuana and other psychoactive drugs. Marijuana is said to have exerted a decisive impact on human evolution because it is able to satisfy H. sapiens' desire for intoxication.

Chapter 4 presents Solanum tuberosum or the potato. A well-developed natural history of the potato, from the Andes to Ireland to Idaho, is presented in an eminently readable format. The potato's impact on various cultures is considered, and modern American farming techniques are discussed at considerable length. The author also presents personal experiences growing and eating various types of potatoes. An additional major topic considers the NewLeaf potato, a patented transgenic organism of the Monsanto Corporation. Portions of the chapter previously appeared in serialized format, and the additional rigor obtained through re-working for the book is evident. The potato is said to have exerted a decisive impact on human evolution because it is able to satisfy H. sapiens' desire for control.