Landfilling is the oldest method of waste management. A number of biological, chemical, and physical reactions occur at the landfills, which cause a threat to the environment. For this reason, landfill monitoring is necessary, and biomonitoring is increasingly beginning to be used. The aim of this study is to (i) determine some effects of the landfill on the surrounding environment, (ii) analysis of plant bioindicators and (iii) biomonitoring based on the occurrence of plant species producing allergenic pollen. Furthermore, plants producing fruits and seeds were also analysed. During biomonitoring, no serious effects of the landfill on the surrounding environment were detected. The plant species found were evaluated based on the frequency of occurrence, pollination vector, distribution of fruits and seeds, and intensity of allergen effects. Thanks to the occurrence of plant allergens, there is a potential risk of the spread of allergens to the landfill surroundings. Furthermore, some species of non-native and invasive plants were found on the active part of the landfill. These species spread their seeds and fruits, and they pose a potential risk to the ecosystems.