The taxonomic history of the three genera Pereskia, Maihuenia, and Blossfeldia is reviewed and discussed in the context of general historical aspects of cactus taxonomy and in view of ongoing discussion on evolution and phylogenetic position of the three genera. Some updates and additional observations complementing earlier monographic treatments of Pereskia and Maihuenia and other papers on all three genera are provided. The appearance of these cacti since 2004 on websites is briefly analysed with selected data retrieved from Google searches. All recognized species are illustrated.