In 2023, the flora of cryptogams and vascular plants, as well as plant communities in the “Suchy Łuk” nature reserve was investigated. The aim of the study was to compare the state of contemporary vegetation with the data contained in the “Plan for Reserve Protection” from 1993, which allowed determination of the directions and nature of the ongoing changes. Additionally, maps of the actual vegetation from the two research periods were created. A total of 72 plant species were found in 1993 and 2023 (50 and 60 species, respectively). Despite the similar number of species in both research periods, a significant changes in the species composition were noted. Twelve of the species previously recorded were not confirmed, and 22 new taxa were identified in the recent study. The most valuable element of the flora was the strictly protected species Drosera rotundifolia. Additionally, 17 partially protected species, mainly bryophytes, were found. In both periods, four plant associations were identified: Sphagno recurvi-Eriophoretum vaginati, Vaccinio uliginosi-Pinetum sylvestris, Molinio caeruleae-Pinetum and Leucobryo-Pinetum. In 1993, two sub-associations were distinguished within the last association mentioned, i.e. a typical one and a sub-association with Rhynchospora alba. However, the latter variant was not confirmed in 2023. Over the 30 years analyzed, the area occupied by the Leucobryo-Pinetum and Vaccinio uliginosi-Pinetum sylvestris associations increased, while the area covered by the Molinio caeruleae- Pinetum and Sphagno recurvi-Eriophoretum vaginati associations decreased. The changes in vegetation indicate a gradual decrease in the area occupied by hydrophilic communities, in favour of phytocenoses associated with less humid habitats. The “Suchy Łuk” reserve is well preserved and no sudden changes in the vegetation that could indicate severe degradation of the peat bog have been recorded over the past 30 years. The main threats to the area are changes in water levels and the gradual encroachment of the peat bog by Pinus sylvestris and Betula pendula. Therefore, the reserve should be subjected to constant monitoring and active protection activities.