Long-term monitoring is pivotal to fully understanding spatio-temporal changes in plant diversity, particularly in protected areas. Here we present a dataset including plant presence and abundance data collected using a probabilistic sampling design in the “Montagna di Torricchio” Nature strict Reserve, central Apennines, Italy. Five surveys were conducted in 35 plots during a period spanning 22 years (2002-2024). The dataset allows to study plant diversity changes over space and time across different habitat types by using statistical inference based on solid sampling theory.