The materials presented in the article supplement the information of “Flora of the middle zone of the European part of Russia” (Maevskiy, 2014) for the floras of Voronezh and Lipetsk Regions. The materials were collected in the period 2007–2020 on the protected areas of Usmansky Bor: in the Voronezhsky State Reserve, its protected zone and in the Federal Preserve “Voronezhsky”. The flora of the Lipetsk Region is supplemented by 9 species: Alchemilla argutiserrata, Aronia mitschurinii, Carex remota, C. tomentosa, Centaurea majorovii, Cotoneaster lucidus, Hieracium sylvularum, Scirpoides holoschoenus, Symphoricarpos albus. The data on 11 new taxa are given for the Voronezh Region flora: Cotoneaster lucidus, Crataegus ucrainica, Hieracium sylvularum, Nymphaea × marliacea, Phytolacca acinosa, Philadelphus latifolius, P. serotina, Spiraea chamaedryfolia, Thuja occidentalis, Veronica polita, Wolffia globosa. The article reports on new finds of Carex bohemica and Prunus cerasifera, species that were previously noted in the region, but not included in “Flora ...” (Maevskiy, 2014). Among the 20 marked species, 11 taxa are alien ornamental plants and fruit trees and shrubs noted outside of cultivation areas. Leaving the places of cultivation by alien plants and naturalization in natural communities is a modern problem of protected areas in the European part of Russia.

Establishment of “blacklists” is one of the attempts to focus on the issue of biological invasions of alien species that pose the most significant threat to regional biodiversity of a certain region. Blacklists contain biological and environmental characteristics and information on invasive species distribution. In Russia, regional blacklists of invasive species are often based on expert opinions or various criteria. For the standardization of alien species information, we propose (1) to use a quantitative assessment of the participation of invasive species in regional floras and plant communities, which makes it possible to evaluate objectively the invasive status of a species and the degree of its impact; (2) to include all invasive species of the region in the regional “Black Books”; and (3) to present potentially invasive species as separate lists. We offer 65 invasive alien plant species for inclusion in the regional Black Book of Voronezh oblast: 9 species are transformers, 20 are actively inhabiting and naturalizing in disturbed seminatural and natural habitats, and 32 are spreading in disturbed habitats. The status of four species is still not defined. Twenty-two species are potentially invasive, because they do not have large spread in the area, but showed themselves as invasive in adjacent regions (in deciduous forests and forest-steppe zones).

The problems of alien plant species invasion into protected nature territories are discussed by the example of the Voronezh Biosphere Reserve. The measures for natural flora and vegetation protection from biological pollution are suggested for the Russian system of protected territories.