From native status to functional traits: Rethinking plant selections in global bioretention guidelines

Bioretention systems are widely used in green stormwater infrastructures due to their cost-effectiveness and ability to reduce surface runoff and pollutants. Vegetation plays a crucial role in these systems, and many stormwater guidelines worldwide highlight the benefits of vegetation in their design. However, it remains unclear whether the guidelines adequately consider the plant selection process and whether this process reflects the current state-of-the-art knowledge of vegetation-related impacts on system performance. This study reviewed 47 stormwater guidelines globally, with most from North America (64 %) and Australia-New Zealand (23 %), and fewer from Europe (4 %), Asia (6 %) and Africa (2 %). The key findings reveal that the highest percentage of guidelines reviewed from North America and Australia-New Zealand suggested using native species in bioretention systems (55 % and 36 %, respectively). However, these guidelines often fail to address plant functional traits and planting strategies adequately. While some guidelines include vegetation lists, these are often optional and do not prioritize functional diversity, which is critical for optimizing system functions. The study concludes that plant origin is a primary consideration in bioretention system design, despite literature not necessarily supporting its significance in influencing performance. To improve bioretention systems efficiency, guidelines must emphasize plant functional traits, diversity and effective planting strategies. Future research should evaluate species based on these criteria to enhance system outcomes. • Native plant focus dominates global bioretention guidelines but lacks performance evidence. • Functional traits like root systems and growth rates are underemphasised in guidelines. • Bioretention efficiency improves with plant functional diversity and trait-based selection. • Non-native species can enhance urban resilience but are rarely considered in guidelines. • Research-informed plant lists are crucial to advancing bioretention system performance.