DNA analysis and morphological observation were conducted for a putative Potamogeton hybrid endemic to the Fuji Five Lakes and Lake Ashi and Potamogeton × leptocephalus from Lake Biwa, Japan. Both proved to be hybrids between P. maackianus and P. perfoliatus. However, the hybrid from the Fuji Five Lakes and Lake Ashi was distinct from P. × leptocephalus in certain morphological characteristics. It is described as a new variety P. × leptocephalus var. fujiensis.
