Considerations for Plant Selection for Sustainable Roof Garden Design in Bangkok

Abstract

Green roofs provide an important means of increasing urban green space, yet clear guidelines for plant selection remain limited. This study examines conditions and constraints influencing plant selection for green roofs in Bangkok. Four case studies located in high-density areas were selected: SiamScape, Samyan Mitrtown, MedPark Hospital, and the Thai Health Promotion Foundation (ThaiHealth). Data was collected through site surveys, plant inventories, and climate observations, along with analysis of rooftop garden design components such as spatial arrangement and planting zones. Interviews with maintenance staff revealed common problems, management processes, and budget considerations, while expert input supported the evaluation of influencing factors. Results show that physical factors including sunlight exposure, substrate depth, and building height play a critical role in plant selection. Areas with greater sunlight and deeper planting media allowed for more diverse species, while steep slopes and extensive hardscape areas posed key limitations for use and upkeep. Most plant species observed could adapt to rooftop conditions, including light, wind, humidity, and pests, which were identified as the most frequent challenges to plant health. However, some species presented risks to building structures. Plant selection must therefore correspond to environmental conditions and site-specific constraints to ensure ecological sustainability. Additionally, social and economic factors, particularly limited maintenance budgets, strongly influenced management. Labor costs were highlighted as a major concern for long-term upkeep. These findings provide a foundation for further research and can inform guidelines for plant selection in rooftop gardens within the context of Bangkok