Selection and Evaluation of Native Plants for Rain Gardens in Tropical Regions: A Dual-Method Assessment Framework

Rain gardens depend on resilient plant species that can withstand fluctuating moisture conditions while providing ecological and aesthetic benefits. This study addresses the limited research on tropical and native herbaceous species by evaluating their health through both visual and physiological assessment methods. A pretest list of 44 species was developed through expert interviews, and plant responses were assessed using chlorophyll fluorescence, expressed as the maximum quantum yield of photosystem II (F _v/F _m), and visual damage ratings after a 15-day continuous immersion experiment. Cluster analysis identified 24 immersion-tolerant species, among which 10 native perennial herbaceous plants were selected for further testing. These species were subjected to repeated water stress cycles consisting of 7 and 14 days of immersion followed by 7 days of drought, repeated over three immersion and two drought intervals. Results indicated that nine species-Aster indicus, Aster shimadae, Lobelia chinensis, Dianthus seisuimontanus, Dianthus superbus, Evolvulus alsinoides, Euphorbia formosana, Lespedeza cuneata, and Richardia scabra-consistently maintained F _v/F _m values above 0.7 throughout both flooding durations, reflecting high photosynthetic stability, indicating that they can tolerate such fluctuations in water availability. By contrast, Eupatorium lindleyanum exhibited F _v/F _m above 0.7 in 66% and 33% of observations in the 7- and 14-day treatments, respectively. These results provide insight into the selection of resilient native species and support the establishment of a standardized methodology for plant health assessment in rain garden design.