This essay examines the scientific research of British naturalists and their Chinese associates in the port city of Canton (Guangzhou) in the eighteenth and early nineteenth centuries. Due to China's strict foreign policy, British research into the horticulture and natural history of China depended heavily on the urban environment of Canton as a global entrepôt. The city was a hub for maritime trade and a contact zone of cultural encounters. The naturalists, who were mostly employees of the English East India Company, broadened their social and commercial relationships with the local Chinese to include scientific inquiry and reconfigured the urban spaces into fieldwork sites. This article discusses the connections between science and urban practices in a maritime entrepôt and proposes revisions to a number of usual assumptions in the current historiography of science and the city.