Congeneric invasive species reduce genetic endemism of native species through hybridization and sometimes cause extinction through genetic or demographic swamping. In the range of Magnolia stellata, a native rare subtree species, Magnolia kobus, an invasive planted/escaped tree species, can also be found. In order to examine possible natural hybridization between the two species, a reciprocal cross-pollination experiment was conducted, and fruit set, seed set, female reproductive success in seed formation (FRS; fruit set  seed set) and seed weight were estimated. With M. stellata as the maternal tree, there were no significant differences in all measurements between intra-and interspecific crosses. With M. kobus as the maternal tree, there were also no significant differences in all measurements except fruit set. These results suggest that there are no reproductive barriers between the two species and planted/escaped M. kobus near the natural habitat of M. stellata presents a threat through hybridization.