The research focused on the evaluation of the growth and development of common reed Phragmites australis and its yield depending on the frequency and time of mowing, as well as hydrothermal conditions in particular years of the study. The foundation for the study was proper classification of the habitat, which is wet meadows. The research confirmed the hypothesis that after mowing, the Phragmites australis does not develop inflorescences in the same growing season, regardless of the time of mowing. Therefore, the presence of old common reed inflorescences in a wet meadow proves that it was not mown last year, assuming mowing after June 15. The height and density of reed shoots and biomass yield depended on hydrothermal conditions, especially on the amount and distribution of precipitation and the groundwater table. Frequent mowing (twice or thrice) stimulated the density of common reed shoots. Such treatments also reduced reed growth, while a single autumn mowing had the least impact on this feature. The development of reed inflorescences was observed to be eliminated by frequent mowing, as well as by mowing performed in the late spring period. On the other hand, throughout the growing season, inflorescences occur only in plots without any treatments and those mown in autumn. The obtained results will help field inspectors to properly assess the controlled wet meadows. For managers and farmers, it will support rational management of common reed cultivation.