The “black list” of the Crimean flora, on the territory of two administrative units - the Republic of the Crimea and the federal city of Sevastopol, is presented. The analysis of the alien species of the Crimean flora was carried out and the most dangerous for ecosystems invasive species of higher plants were identified in accordance with the recommendations for keeping the Black Books. The data on distribution, habitats and invasive status (IS) of 70 species are summarized. Transformers are represented by 9 species with IS 1 ( Ailanthus altissima, Bupleurum fruticosum, Elaeagnus angustifolius, Fraxinus ornus, Jacobaea maritima, Opuntia engelmannii subsp. lindheimeri, O. fragilis,O. humifusa, Rhamnus alaternus ), they change the appearance of ecosystems. Nineteen alien species actively disperse and naturalize in disturbed semi-natural and natural habitats (with IS 2) and 42 species (with IS 3) are widely distributed in disturbed habitats. The peculiarity and variety of soil and climatic conditions of the peninsula contribute to the introduction of alien species, many of which are invasive only on the territory of the Republic of the Crimea and the city of Sevastopol. This article is a necessary step towards the preparation of the Black Book of the flora of the Crimean Peninsula and the basis for making decision on prevention the economic and environmental damage of the natural biodiversity of the region.
