Vegetalismo is the healing and visionary tradition of the mestizo river towns of the Peruvian Amazon, most thoroughly documented around Iquitos and Pucallpa by the anthropologist Luis Eduardo Luna. Its practitioners, vegetalistas, hold that certain plants are teachers rather than mere materials: a madre, a plant spirit or plant mother, is understood to reveal itself to a person who approaches it correctly and to pass on both healing knowledge and the songs, icaros, needed to use it. Ayahuasca, the vine Banisteriopsis caapi taken together with an admixture leaf such as chacruna, is the tradition's central plant teacher and the sacrament of its principal ceremony, but it is one master plant among many rather than the whole of the practice.
The route to becoming a vegetalista is the dieta, a period of isolation on a restricted, largely bland diet, without salt, sugar, alcohol or sexual contact, undertaken while ingesting a chosen plant teacher over days or weeks. Practitioners describe the dieta as the actual site of learning: the plant is said to teach directly, in dreams and in the icaros a dieter comes away singing, rather than through any human instructor explaining technique. A vegetalista's authority and reputed skill rest on the plants he or she has dieted and the icaros received in the process, a curriculum that is personal and plant given rather than institutional. The atlas describes this structure of belief and practice; it does not set out how a dieta or a ceremony is conducted.