Assessing growth performance and deficiency of climber species on tropical greenwalls

• 10 mesh-climbers and 10 concrete-climbers were chosen for field planting experiments.
• Climber growth performance and defects were monitored from seedlings for 32 months.
• Climber performance index provided guidelines on species choice and greenwall design.
• Climber defect index identified growth problems to help species choice and management.
• Excellent performers are Quisqualis indica, Wisteria sinensis and Lonicera japonica.

Vertical greening can contribute to urban green infrastructure, urban heat-island amelioration and climate adaptation. Tropical greenwall practice, hindered by inadequate scientific knowledge and experience, can benefit from objective assessment of species performance and growth deficiency. Comprehensive survey of critical climber-plant traits shortlisted 20 potentially suitable species. A climber-selection matrix was established to facilitate species selection and greenwall design. Perennial woody climbers with ornamental flower or foliage and biological potential to reach 13-m height were preferred. They represented two attachment modes, namely mesh-climber and concrete-(bare-wall)climber groups. A field study was designed to monitor their growth from seedlings in experimental plots. Growth conditions were optimized by providing high-quality soil mix and irrigation. The 32-month study period included three active-growing seasons with two interspersed slow-growing seasons. Field assessment methods were developed to acquire systematic data on plant performance indicators and deficiency symptoms. Key attributes were selected to compute climber performance index (CPI) and climber deficiency index (CDI) as synoptic representation of greenwall-application suitability. Mesh-climbers performed much better than concrete-climbers across all key performance indicators, and with notably better CPI. They demonstrated faster establishment and growth rates and more ornamental flowers. The two groups had similar CDI mainly due to insufficient foliage density and foliage loss. For mesh-climbers, Quisqualis indica, Wisteria sinensis and Lonicera japonica had excellent performance, and the remaining species were good to fair. For concrete-climbers, only Parthenocissus dalzielii was rated good and Campsis grandiflora fair, with the rest poor to very poor.