The Baja California Peninsula and surrounding landmasses harbor an abundant flora in an otherwise harsh and arid environment. Of the many plant groups native to this peninsular and insular region, passionflowers (Passiflora, Passifloraceae) are represented by a handful of taxa that all belong to a single lineage within the genus (section Dysosmia). Despite centuries of exploration and floristic research in the area, basic questions remain regarding this group—particularly the taxonomic status among the Passiflora arida complex. Using an extensive sampling of herbarium specimens and iNaturalist observations, the claims of endemism, habitat characteristics, and taxon boundaries were investigated. Peninsular endemism was confirmed for only one of the native Passiflora taxa (P. fruticosa), with an additional taxon (P. palmeri) considered near-endemic. Soil and climatic data revealed significant distinctions between the habitats of many of the native taxa as well as within the P. arida complex, corresponding mostly to precipitation and temperature variables. Geometric morphometric analyses showed little success in separating taxa based on leaf shape, indicating this line of evidence may not be a good indicator of taxon identity in this group of plants. Based on ecological differences and discrete macro- and micromorphological features, a varietal name is here synonymized and a new combination is proposed: Passiflora pentaschista.