The dynamics of reproductive allocation (RA) in herbaceous plant communities, particularly in response to varying environmental conditions such as drought stress and competitive interactions, remain underexplored. This study aims to fill this gap by hypothesising that both belowground resource limitation and the presence of dominant species significantly influence RA strategies within plant communities, leading to different patterns of reproductive synchrony. We also expected different effects of resource limitations on intraspecific synchrony in RA compared to interspecific synchrony. We conducted a mesocosm experiment in an experimental garden over five years, exposing wetland plant communities (one dominant species and three subordinate species) to different drought stress regimes and a dominant removal treatment. The results suggested that belowground resource limitation and aboveground competition critically influence RA synchrony, with increased synchrony under reduced competition and increased stress. The competitively dominant species require more belowground resources for seed reproduction, while competitively weaker subordinate species can reproduce at lower resource levels. Furthermore, our findings highlighted contrasting responses in intra- and interspecific flowering synchrony to the resource limitations, which may reflect the different importance of evolutionary synchronising factors and competitive and facilitative effects between conspecifics and between species within the community. Individuals of species synchronised flowering mainly at their favourable sites where generative reproduction is more efficient, i.e. dominant species at wet sites, whereas subordinate species at drought stress treatments with reduced competition. This research provides empirical evidence for the multiple resource limitation model and highlights the strategies of plants in resource-limited environments, as well as the ecological importance of reproductive synchrony within herbaceous plant communities.