The hybrid Polystichum × arendsii was first bred by Georg Arends at the turn of the 20th century. It was an artificial cross between P. munitum (Kaulf.) C. Presl, native to north western North America, and P. aculeatum (L.) Roth, occurring in the Eurasian region. In 1906 the well-known Swiss botanist Konrad H. Christ applied the name Aspidium × arendsii to this hybrid. In the following decades the fern was lost and its name was forgotten. The present study investigates the history of the hybrid. In the interim, the cross has been successfully carried out once again and a new description of P. × arendsii is provided. Study of herbarium material and comparison of the information supplied by Konrad H. Christ, as well as the analysis of the spores, confirmed that the hybrid corresponds with the original A. × arendsii and a necessary valid combination under Polystichum is provided.