This study presents a floristic and vegetational analysis of the territory of the Onferno Nature Reserve. The site extends over about 120 hectares, and is located in central Italy, in a hilly area near the Adriatic coast. It is characterised by the presence of large gypsum blocks that have karst caves, where important colonies of bats lives. This study of the vegetation allowed the description of six main vegetation series, divided into three different geosigmeta: a geomorphological unit of gypsum substrata (Gessi di Onferno); a geomorphological unit of clay substrata (Formazione del Santerno); and a geomorphological unit of compact sandstone substrata (Formazione Montecalvo in Foglia). This floristic and vegetation studies carried out on the secondary grasslands (EC Habitat 6210) have allowed the evaluation of the grazing effects on the conservation of their biodiversity, and highlight the critical nature of this management method. Furthermore, on the basis of the vegetation studies, the list of habitats according to EC Directive 92/43/CEE has been better defined and updated.