Urban stormwater ponds are important for flood protection and provide habitat for plants and animals in heavily sealed cities. Little is known about the diversity of plants in urban stormwater ponds and the vegetation composition is often influenced by sowing and planting. We analysed the re-colonisation of the vegetation in an urban stormwater pond, which was reconstructed to improve water retention. Specifically, we studied if the soil seed bank has the potential for re-colonising the pond. We analysed the standing vegetation from the year before until 2 years after reconstruction of a stormwater pond in Hamburg, Germany. Further, we analysed the soil seed bank in the year before and in the second year after reconstruction of the stormwater pond. We found 74 species in the soil seed bank in 2015 and 2017 with Juncus spp. and Epilobium spp. being the most dominant taxa. Our results indicate that urban stormwater ponds have the potential for re-colonisation out of seed bank and, thus, sowing is not a necessary management action in the reconstruction process.