From ancient to local knowledge about the root system of plants in Europe and in the colonies (16th-18th c.) ABSTRACT Did the arrival of foreign and exotic roots from the colonies radically change local practices and customs ? The presentation will explore the construction of botanical knowledge in Europe and the colonies, through multiple examples of the root system of plants and the relationship to their place of growth. Since the 16th century, the conception of the plant has been based on the theory of the galenic humours. This universal model distinguished plants according to their therapeutic virtues and roots were particularly used for their laxative and purgative, hot and dry qualities. The root was a discriminating criterion that made it possible to identify and name a plant after its harvest. Observers, physicians and naturalists of early modern times, began to examine local plants, in their own country or abroad. They questioned the ancient knowledge of plants and their roots, in the texts of Galen, Dioscorides, Pliny the Elder or Theophrastus. Direct observation systematically changed the naturalist's view of the territory of plant growth, and a complex notion of "environment" was introduced. In spite of everything, the theory of humours and some stereotypes linked to the natural elements (water, earth, air, fire) remained prevalent. The roots of plants, consumed as medicine and food, were the focus of attention until the middle of the 18th century. For physicians, the roots are the organs that, close to the earth, collect underground resources and keep the plant alive. These epistemological transformations did not prevent certain beliefs from persisting.