<p>Decentralised bioretention systems are Nature-Based Solutions that have proven their ability to manage urban stormwater runoff, both quantitatively and qualitatively. In recent years, several studies have suggested that the contribution of vegetation to stormwater pollutant removal could be enhanced and that better biofiltration could be achieved by selecting plants according to their biological characteristics or functional traits. The aim of this work was to provide a synthesis of the existing information on the way in which plants affect, or have the potential to affect, the biofiltration capacity of decentralised bioretention systems, while providing perspectives for future research. It emerged that vegetation can play an important role in the functioning of the bioretention ecosystem, but that its functional diversity could be better exploited to optimise biofilter performance and resilience to environmental stressors. As expected, the root system emerged as the main actor in the pollutant treatment due to its intrinsic biophysical properties, but also due to the microbial communities it can host. The use of more systematic trait-based approaches and long-term field studies would be required to elucidate the contribution of plant functional diversity and to provide more evidence-based decision support tools for proper bioretention design and management. Finally, more explicit integration of plant ecophysiological traits and their ecological strategy in relationships with soil microbiota should help to improve plant species selection and overall bioretention ecosystem services related to water and soil quality.</p>