This essay describes the emergence of "hormone" herbicides from academic plant physiology research in America in the late 1930s and 1940s, attending especially to the role of interactions between university scientists, industrial concerns, and government (particularly agricultural) agencies. The importance of an intellectual shift among the physiologists to viewing hormones as plant toxins rather than growth stimulators, spurred by wartime events, is discussed. The essay concludes by exploring the postwar marketing of these hormones as agrichemicals and as lawn treatments for suburban consumers, placing these in the economic and ecological context of other contemporary developments in farming technique.