The artificial peatland on Notre-Dame Island (Montreal, Québec) was created 35 years ago using blocks of peat collected from a peatland in the James Bay (Québec) area that was destined to be flood and lost. This study investigates the changes in the species composition and functional traits of the flora that have occurred since the site was established. There was a 48% decline in species richness between 1979 and 2014, together with a significant increase in the number of exotic, generalist and meridional species. Only 5 of the 56 species that were originally present in 1979 were found in 2014. Significant changes were also observed in the requirements of the plants present in 1979, compared to those of the plants present in 2014. The needs in terms of substrate acidity, moisture and organic matter content, and the light tolerance of the plants, have decreased significantly since the site was established. By contrast, the average soil nutrient requirements have increased significantly. These changes indicate that the site is becoming less and less characteristic of a peatland. A number of suggestions are proposed for improving the success of wetland compensation projects.