Cyperus polystachyus Rottb. is a threatened species occurring in Europe only in two sites located in wetland habitat in mediterranean Southern Italy. According to the IUCN red list for Italy (1997), the species is listed as critically endangered (CR). This study investigated recruitment and habitat limitations referred to the population located south of Rome, in the Tor Caldara Regional Reserve. The site is an isolated island of vegetation. Natural expansion of the species is highly limited by the absence of “wet” sites in the surroundings. Importantly the study also endorsed an “in wild translocation program”, which aimed to decrease the risk of species extinction linked to demographic stochasticity, extreme climatic events or mismanagement. Seed germination, seed and site limitations, and germplasm translocation were investigated. Seed viability and seed germination were tested at the Rome Botanical Garden; results showed that the species has high recruitment potential, especially in thermophilous conditions. Germplasm (seeds) was translocated in a vegetation remnant within the Protected Area of Decima Malafede overseen by RomaNatura, a Regional Agency for the management of PAs, which, together with the National Environment Research Institute (ISPRA) was one of the partners in this research. The site limitation and translocation studies were undertaken in a glade with a seasonal pond. Seeds were sown and seedlings planted within an experimental framework, protected by a metal cage to prevent grazing. The new site is within the natural dispersion range of the species in an area with similar ecological and biogeographic conditions. It is surrounded by thermophilous oak woodland and cultivated fields which exclude germplasm escape. Results showed that, due to the germination behaviour, the establishment is limited by the absence of microsites suitable for recruitment. Competition with perennial species and delayed germination are the main obstacles for recruitment, especially during prolonged drought episodes under climatic changes. Short-term assessment of the translocation process was undertaken. Values of new seed set, seed viability and germination were similar to those present in the original site. Translocation was, consequently, proved successful until this first stage. Outcomes will be useful both for the conservation of the species and for the production of an Italian handbook for ex situ conservation of threatened species. It is hoped that monitoring, ongoing care and evaluation will continue to be carried out also in the future.