The genetics underlying Cyto-Nuclear Incompatibility (CNI) was studied in Pelargonium interspecific hybrids. We created hybrids of 12 closely related crop wild relatives (CWR) with the ornamental P. × hortorum. Ten of the resulting 12 (F₁) interspecific hybrids segregate for chlorosis suggesting biparental plastid inheritance. The segregation ratios of the interspecific F₂ populations show nuclear interactions of one, two, or three nuclear genes regulating plastid function dependent on the parents. We further validated that biparental inheritance of plastids is common in section Ciconium, using diagnostic PCR primers. Our results pave the way for using the diverse species from section Ciconium, each with its own set of characteristics, as novel sources of desired breeding traits for P. × hortorum cultivars.