This article presents an assessment of the systematic and quantitative composition of a collection of rare plant species, a study of their seasonal growth and development patterns, and their reproductive potential upon introduction to the middle taiga subzone of the Komi Republic. It is demonstrated that some of the rare plant species studied exhibit irregular fruiting and produce defective seeds. The primary focus of the collection of rare and endangered plants at the Botanical Garden of the Institute of Biology, Komi Scientific Center, Ural Branch, Russian Academy of Sciences, is on species included in the Red Book of the Russia and the Red Book of the Komi Republic. Currently, more than 100 specimens of more than 70 species belonging to 33 families and 53 genera are being studied in the collection of rare herbaceous perennials. The collection is dominated by rare species with rarity status category 3: more than 50% of species are from the Red Book of the Russia and more than 70% of species are from the Red Book of the Komi Republic. Changes in both the species composition and the number of species in the collection of rare herbaceous perennials are noted. Currently, the Botanical Garden boasts the greatest diversity of species in the families Ranunculaceae, Caryophyllaceae, Orchidaceae, Paeoniaceae, Iridaceae, and Liliaceae. In addition to flowering plants, six species of rare ferns from the families Aspleniaceae, Dryopteridaceae, Polypodiaceae, and Thelypteridaceae are cultivated.