The worldwide use of ayahuasca, an entheogenic tea originally used in ceremonial context by Amazonian peoples, has increased in the last decade. In Brazil, “seringueiros” or rubber tappers have incorporated its use into urban settings, creating three main religions that continue to drink the sacred tea: Santo Daime, Barquinha, and União do Vegetal. A neo-ayahuascan network has arisen along with the expansion of ayahuasca, with distinct meanings associated with the tea, including using it for therapeutic, artistic, religious, and playful purposes. Brazilian ayahuascan groups (BAGs) commonly prepare the tea using the stems of Banisteriopsis caapi (Malpighiaceae) along with the leaves of Psychotrya viridis (Rubiaceae) or sometimes with those of Diplopterys cabrerana (Malpighiaceae). There are citations of traditional Amazonian peoples using the stem of other Malpighiaceae species to prepare ayahuasca in the literature, also several papers refer to “ethnotaxa” of B. caapi recognition. Fertile samples must be collected in order to identify genera and species of Malpighiaceae, which is not always possible due to the short flowering period. There is also a difficulty in collecting sacred plants due to access limitation inside the traditional communities, and due to the natural obstacles in liana sampling in the Amazon Forest. Data in the literature shows that wood anatomy is a good tool to identify plants. Our study synthesizes ethnobotanical material and wood anatomy data in order to understand: (1) whether there is consensus between the respondents of the BAGs of the identity of ethnotaxa; (2) whether there is a hierarchical classification of the ethnotaxa, and whether it can be described and reproduced, illustrating the variation of B. caapi in more detail; (3) whether stem anatomy can be used to distinguish the genera and ethnotaxa used in the production of ayahuasca; and (4) whether there is homogeneity in the use of ethnotaxa or if any of them is more commonly used. Thirty-eight people belonging to BAGs were interviewed. Eighteen ethnotaxa and 30 names for B. caapi were documented. Among the respondents, there are disagreements about the ethnotaxa identities. There is an ethnotaxa hierarchical classification based on stem morphology, which groups them as lianas with swollen nodes (caupuri) and without swollen nodes. However, the tea chemical effects are equally important, as there are lianas called caupuri which do not have swollen nodes, but have the same effect. Wood anatomy and morphology can help in understanding the categorization of ethnotaxa. Stem wood anatomy was also used to verify the identity of Diplopterys cf. pubipetala, which was cited by one respondent. Some ethnotaxa are more used for their chemical effects or their ease of cultivation. Our data suggest that B. caapi has some degree of domestication and that BAGs help to maintain a significant portion of B. caapi diversity. The role of these groups as plant “guardians” used to make ayahuasca is unique at this historical moment, in which the Amazon rainforest and its great diversity is being cruelly and irresponsibly decimated.