Towards More Resilient Urban Landscapes: Optimal Sowing Season of 16 Native Mediterranean Species for Planting Designs

Cities increasingly face the impacts of global change, demanding innovative approaches in species selection and management to create more adapted and resilient urban landscapes. The incorporation of native Mediterranean flora into planting design offers an opportunity for certain Mediterranean cities to achieve this by selecting species according to their ecological feasibility and aesthetic impression throughout the year. This study constitutes a first step towards understanding the germination behaviour of 16 native Iberian plant species, with potential for use in urban planting through direct seeding. Species were selected for their ecological feasibility in Mediterranean urban environments and to maximise functional diversity in growth forms, phenology, and other vegetative and reproductive traits, thereby supporting biodiversity and ecosystem resilience. Controlled germination trials were used to evaluate germination percentage and mean germination time of 16 species under temperature and light conditions that simulated autumn and spring, the main Mediterranean germination seasons, and spring-like conditions following cold stratification. The results revealed variability in seed germination among scenarios and species, indicating diverse and contrasting germination strategies. The majority of species achieved their highest final germination percentage under the autumn scenario. Germination speed was also strongly scenario-dependent, with several species completing germination within 10 days, and cold stratification reducing the mean germination time of the most responsive species. Based on these findings, a functional classification is proposed to guide the optimal sowing season. Although autumn appears to be the most favourable time for seed sowing, species-specific germination patterns must be considered to ensure successful establishment and the effective inclusion of each species in seed mixtures.