The Seven Lakes Nature Preserve comprises nearly 2,400 hectares of aquatic, wetland, and upland habitats in southeastern Alger and northeastern Schoolcraft counties in the eastern Upper Peninsula of Michigan. The preserve was obtained and protected by the J.A. Woollam Foundation and has undergone several expansions. In an area of Michigan with relatively limited development and few roads, the natural communities of Seven Lakes are highly intact, and many of its habitats have recovered since the historic logging era. Botanical surveys were conducted in 2016, 2017, 2020, 2021, and 2022 with the goals of describing the natural communities and ecosystem processes and of producing a comprehensive floristic inventory. The post-glacial natural history of the region and a description of climate and soils are provided. A floristic quality assessment was performed, yielding a Total Floristic Quality Index of 99.9, a Total Mean C of 4.5 and a Native Mean C of 5.3. Within the upland forests, shrubby and forested wetlands, and open wetlands, eleven plant communities are described following the classification system proposed by the Michigan Natural Features Inventory. The floristic affinities of rare or otherwise noteworthy taxa are discussed, as are potential threats to the ecosystem. Four-hundred ninety-three species and four hybrids were observed during our surveys, 147 species are represented by specimen vouchers and 440 are recorded as photo vouchers on iNaturalist. Sixteen new species records for Alger County are reported.