Ecologically inspired green walls: addressing structural and biological barriers through novel substrate design – an experimental trial

Background Green walls face key barriers to adoption, including water inefficiency, structural limitations and poor plant survival in arid climates.Aims This study addressed these gaps by (1) developing a bio-inspired design based on field analysis of spontaneous vegetation on ageing walls in Iran, Austria, Slovakia and France and (2) creating a novel lightweight substrate optimised for vertical ecosystems.Methods Four substrate compositions were engineered by mixing polyvinyl alcohol (PVA: 9.5–40%), silicon dioxide (20–28%), perlite (20–30.5%) and cellulose (20–31%). The suitability of the substrate mixes was compared with germination assays and follow-up test established substrate suitability for water retention and plant growth.Results Under simulated arid conditions, Lepidium sativum achieved 95% germination in Mix 3 (9.5% PVA, 28% SiO2, 30.5% perlite, 31% cellulose, pH 6.33), significantly better than in Mix 1 (40% PVA; 40% germination; p < 0.001). Field validation using five drought-tolerant native species confirmed the suitability of the substrate. Plant survival was 92% over a 4-week establishment trial in the presence of a reduction of 40% in watering frequency.Conclusion By integrating ecological knowledge with material innovation, this research demonstrates the initial potential of a scalable, resource‑efficient vertical greening system for climate‑resilient cities, pending long‑term field validation.