With the accelerated process of urbanization, air pollution has become increasingly severe. Garden plants can trap atmospheric particulate matter, which is of great significance for improving the urban ecological environment and promoting sustainable development. To investigate the dust retention effect of typical transportation green spaces in Nanjing, this study focuses on thirteen garden plants on Xuanwu Avenue in Nanjing. The dust retention capacity of these plants was determined using the wash-off method, while the microstructure of their leaf surfaces was observed using scanning electron microscopy. The results are as follows: Firstly, per unit leaf area, Liriope spicata, Ophiopogon japonicus, and Viburnum odoratissimum demonstrate solid dust retention abilities. Additionally, Viburnum odoratissimum, Prunus serrulata var. Lannesiana, and Liriope spicata show strong dust retention abilities per single leaf. Moreover, Platanus acerifolia, Viburnum odoratissimum, and Cinnamomum camphora have strong dust retention abilities per plant. Viburnum odoratissimum, Platanus acerifolia, and Prunus serrulata var. Lannesiana exhibit the most substantial dust retention capacities. Secondly, there is a significant negative correlation between dust retention per plant and the potassium content, while a significant positive correlation is observed with plant height, canopy height, and leaf width. Furthermore, there is a highly significant positive correlation between dust retention per unit leaf area and stomatal length and a highly significant negative correlation with leaf length. The surface microstructure of the blade mainly increases the dust retention capacity of the blade by increasing the friction of the leaf surface. Lastly, specific leaf surface microstructures, such as grooved epidermis and trichomes, enhance plants’ dust retention capacity. Consequently, for the future configuration of road green spaces in Nanjing, a mixed planting mode of trees, shrubs, and grass is recommended. Priority should be given to selecting plants with strong overall dust retention capabilities, such as Platanus acerifolia, Viburnum odoratissimum, and Prunus serrulata var. Lannesiana, to alleviate air pollution, improve the urban ecological environment, and achieve sustainable development.

Urban vegetation can act as an effective sink for airborne particulate matter (PM) in densely populated cities, yet how specific leaf functional traits regulate the retention of different PM size fractions remains poorly resolved. In particular, it is unclear whether fine and coarse particles are governed by similar trait mechanisms under realistic urban roadside conditions. Here, we examined 44 common roadside plant species along roads with contrasting traffic intensity and surrounding land-use characteristics in Nanjing, China. Foliar retention of multiple PM size fractions (total suspended particles, PM >10 μm, PM10-3 μm, and PM3_-1 μm) was quantified using a three-stage membrane filtration method, together with measurements of leaf functional traits and surface micromorphology. PM retention capacity differed significantly among species and life forms (p < 0.05). Retention of coarse particles was primarily associated with structural traits that enhance mechanical interception, whereas fine-particle retention was more strongly linked to micro-scale leaf traits, particularly stomatal width, indicating a clear size-dependent shift in trait importance. Although particle-size distributions varied among roadside environments, trait-PM relationships remained broadly consistent across sites. These findings demonstrate that particulate matter retention by urban vegetation is regulated by distinct, size-dependent trait mechanisms rather than by a uniform set of functional traits. By highlighting functional specialization in plant-PM interactions, the present study provides a trait-based framework for optimizing urban roadside vegetation design according to local pollution profiles and mitigation objectives.