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

Abstract

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.