Revegetation decisions have genetic consequences: actively and passively restored salt marshes display different genetic diversity and composition

Genetic diversity facilitates common restoration goals like creating resilient and adaptable populations. Yet, the genetic consequences of restoration are rarely considered. To inform and motivate the inclusion of genetic diversity into restoration decision‐making, we assessed the genetic diversity of the salt marsh foundation species Spartina alterniflora in three types of salt marshes: actively planted restored sites, passively colonized restored sites, and natural marshes. We found that active restoration was associated with higher genetic diversity, whereas passive restoration and natural marshes were equivalently associated with lower genetic diversity. All three marsh types had disparate genetic composition, but only actively restored sites contained seemingly non‐local genotypes. These distinct genetic outcomes likely have proportionally distinct implications for eco‐evolutionary processes. Our work adds to growing evidence that genetic diversity can be influenced by restoration decisions and should therefore be considered during restoration planning and in restoration policy.