Using Recycled Glass Substrate for Seed Germination in 17 Common Coastal Dune and Maritime Plants

Allen, K.E.; Hammer, T.G., and Henning, J.A., 2026. Using recycled glass substrate for seed germination in 17 common coastal dune and maritime plants. Journal of Coastal Research, 42(4), 644–653. Charlotte (North Carolina), ISSN 0749-0208. Restoration of coastal dunes to combat erosion often requires renourishment of sand substrate dredged from offshore sources, although dredging has well-described negative ecological impacts and high economic costs. Recycled glass sand (cullet) made from crushed glass bottles has been proposed an alternative substrate to replace offshore dredging. However, glass sand substrates may have limited ability to support plant communities because of the absence of an established native soil microbial community. Although several studies have highlighted the ability of glass sand to support the growth of transplanted plants, the ability of glass sand substrate to support seed germination of native coastal taxa has not been explored. To simultaneously explore the impact of substrate and native microbial communities, a factorial seed germination experiment was conducted using 17 common coastal dune and maritime plant taxa. Overall, the experiment found no difference in seed germination between glass sand and natural beach sand substrate and that native microbial addition reduced the overall seed germination rate by about 5% on average (36.7% no microbe vs. 31.9% microbial addition); however, some late-successional species, such as Asclepias humistrata and Iva imbricata, benefited from soil microbes. Species identity was the strongest predictor of seed germination success overall, which was positively correlated to seed size. Taken together, the results suggest that dune renourishment projects with recycled glass sand should support secondary succession of late-successional dune and maritime species, lending further support on the efficacy of glass sand as a viable alternative substrate to dredged sand substrate.