Sown and self-seeding species in planted wildflower meadows increase floral abundance and richness in a Scottish semi-natural coastal grassland

Background Reduction in available floral resources has contributed to global pollinator decline. Suitably managed urban habitats can provide high floral resources, with potential to support pollinator populations. Here we quantify the consequences of planting native wildflower meadows in peri-urban unimproved coastal grassland in Edinburgh, Scotland.Methods We compared seasonal patterns in floral abundance, richness, and composition between eight replicate sown native wildflower meadows and eight paired semi-natural grassland plots over three years (2021–2023). We distinguished contributions of planted (sown seed mix) and unplanted (self-seeding, non-seed mix) species in planted meadows.Results We surveyed a total of 191,642 floral units of 72 species. Meadow and grassland plots showed significantly different seasonal phenologies and between-year variation in flowering species composition. Many species absent from the sown seed mix (including most surrounding grassland species) also flowered in the meadow plots, contributing to significantly higher overall meadow floral species richness. Floral abundance was significantly higher in planted meadows, and higher in seed mix than non-seed mix species.Conclusion Planted native wildflower meadows offered consistent enhancements to floral richness and abundance, through both planted and unplanted species. Contrasting compositions and phenologies of grassland and meadow flower assemblages provide a greater diversity of trophic rewards for pollinators than either would alone.