Abstract Urban growth contributes significantly to biodiversity loss. Finding creative solutions to promote biodiversity and provide habitat space is thus an urgent need in urban areas. Underutilized green infrastructure, such as street tree beds, offers potential to support diverse plant life in cities. This study explores whether citizen stewardship of these beds enhances urban plant diversity and alters species composition. Vegetation surveys were conducted in 200 street tree beds–pairs of 100 stewarded and 100 non-stewarded—in Freiburg im Breisgau, Germany, assessing vascular plant diversity alongside factors such as tree diameter, bed size, and surface sealing. Results showed that stewarded beds supported significantly greater species richness and more diverse plant communities, primarily due to a higher number of gardened species, though native species richness was also higher. Both stewarded and non-stewarded beds contained native ruderal species. These findings underscore the value of citizen stewardship in promoting urban biodiversity by creating habitats that blend cultivated and native plants. This research highlights a still little-used opportunity for cities to promote biodiversity and engage residents directly in nature-based solutions. These citizen-led efforts increase local biodiversity and provide accessible, daily opportunities for urban dwellers to connect with nature, improving well-being and supporting broader policy goals for livable, healthy, and resilient cities.
Heid et al. (Thu,) studied this question.