Abstract Peatlands can be degraded by mining and smelter emissions, with severe impacts on Sphagnum mosses, the key peat‐forming species in many bogs and poor fens. While restoration of horticulturally extracted peatlands is common, less is known about restoring smelter‐impacted peatlands, such as those in Sudbury, Ontario. In 2019, 30 10 × 10 × 10 cm Sphagnum moss–peat plugs representing five species were transplanted into a denuded, smelter‐impacted peatland. Transplant survival and plug dimensions were recorded from 2019 to 2024. After 2 years, one designated destructive plot was sampled for exploratory chemical and microbial analyses. Transplant responses varied strongly among species. Sphagnum fuscum and S. fallax showed the strongest establishment, with S. fuscum plugs reaching mean dimensions of 25.5 × 25.3 cm by Year 5 and S. fallax colonizing patches outside the original plugs. Sphagnum medium survived but persisted at reduced size, while S. cuspidatum and S. palustre failed to establish. Exploratory chemical and microbial data suggested that transplanted moss–peat plugs accumulated metals after placement in the host peatland, while retaining some donor‐associated microbial signal after 2 years. Because destructive sampling was limited to one plot, these patterns are interpreted as descriptive context rather than formal tests of transplant effects. Practical implication . This trial provides encouraging evidence that Sphagnum transplantation can contribute to restoration of smelter‐impacted peatlands, but establishment depended on species identity and microsite position. Future restoration should prioritize species–microsite matching, with S. fuscum and S. fallax as promising initial candidates, rather than applying donor material uniformly across damaged peat surfaces.
