The genetic diversity of a population has wide-ranging and often positive impacts on ecosystem functioning. Seagrass meadows are highly productive marine plant ecosystems and reproduce both sexually and asexually, yielding different levels of genetic diversity which can influence responses to anthropogenic change. Here we investigate the genetic diversity, via microsatellite amplification, of the shoalgrass, Halodule wrightii across three different sites, in two different years, in North Carolina. H. wrightii is a tropical seagrass that has expanded northward as water temperatures increased. We found that H. wrightii was extremely clonal: of the 149 shoots sampled, 145 (97.3%) belonged to the same clone and this clone remained unchanged between years. These patterns indicate that edge-of-range seagrass populations harbor less genetic diversity and reproduce primarily asexually. Thus suggesting that the most well-adapted genotype has been maintained over time. Understanding the genetic composition of these key habitat-forming organisms can strengthen restoration and conservation practices.