Supporting pollinators in urban gardens: floral richness and abundance influence flower visitor interactions regardless of the surrounding landscape

Private gardens contribute to a large area of land within cities. Yet, little is known about the value of private gardens in pollinator conservation in terms of their management and position within the urban matrix. We investigated seasonal patterns in how environmental variables influenced plant-flower visitor interactions and the network structure in private gardens. We collected plant-flower visitor data in 18 private gardens, across Glasgow, Scotland, simultaneously recording floral abundance and richness, plant origin, garden size, land use diversity and the area of green space surrounding gardens. We observed a decline in native plant abundance from June until September, but flower visits to native and non-native plants did not track this seasonal pattern. Flower visits to native and non-native plants differed depending on whether visits were analysed at the community or plant species level. Furthermore, increasing non-native floral abundance showed a greater increase in flower visitors compared to when native floral abundance increased. Plant-flower visitor networks varied seasonally, becoming more specialised in June and September, but were not influenced by other environmental variables. Overall, higher floral richness and abundance within a garden influenced flower visits, independent of the surrounding landscape. Our results indicate that private gardens can support pollinators in cities, regardless of the urban context in which they are situated and that pollinator diversity may be improved in gardens by increasing floral diversity. We provide a list of attractive plants species to help inform floral plantings in gardens.