The authors’ data on the weed species composition in 8 geographic regions of the Russian Federation were laid at the basis of this survey. The segetal flora comprised weeds of cereals, root crops, and perennial grasses. The composition and taxonomic structure of weed species were analyzed. The total number of weedy plants encompassed 686 plant species. The level of regional weed species diversity was positively related to the area planted. Altai Territory, Udmurtia, and Rostov Province had the greatest weed species diversity, with more than 300 species, while Vologda Province had the lowest diversity (193 species). Most species-rich plant families (Asteraceae Dumort., Poaceae Barnhart, Fabaceae Lindl., Brassicaceae Burnet), genera (Potentila L., Artemisia L., Veronica L., Chenopodium L., Silene L., Trifolium L.), their subsequences, contributions of singlespecies families (17–39%) and genera (57–74%) were relatively stable systematic structure indicators. Only 18% of the species were common for all the regions. In each region there were region-specific groups of species. Weed species compositions in geographically close regions – the European part of Russia and the Urals – showed the greatest similarity. As for geographically distant regions (Altai Territory and Rostov Province), their weedy species compositions were distant and contained large groups of region-specific species.

The adventive fraction of the Middle Ural flora is represented by 328 species of vascular plants from 198 genera and 51 families. Most of the adventive plants are nonaggressive and form the group of e

An overview of Russian literature sources of urban flora studies. The authors analyze the history of urban floral research in Russia and provide definitions of terms – urban flora, native, indigenous, apophytic, alien, synanthropic species. The overview provides a description of methods and approaches used in different studies of urban flora. Special attention is paid to the analysis of the biological diversity of native and alien plants and the features of their spatial distribution in urban habitats. The authors raise problems of protection of biodiversity in cities and show the role of urban protected natural areas. The conclusion of the work outlines the prospects for further study of urban flora. The authors highlight an importance and necessity of creation of a unified database of vascular plants in the urbanized territories of Russia. Further usage of the database will allow to conduct a comparative analysis of the species composition of urban flora and to identify the degree of their homogenization and originality.

An analysis of data on the species abundance of flora in 89 cities (urban flora) of the Russian Federation facilitated determination of its main factors. It has been revealed that the factors determining the abundance of native and alien components of urban flora vary. The city area and population number are the main factors of the total number of species and of the abundance of native species in urban flora. The diversity and participation of alien species increase in parallel with. the urbanization rate, anthropogenic transformation of the regions, and the age of cities and are in adverse correlation with the climate severity.

Weeds are plants that, although not specially cultivated, grow and often adapt to growing in arable lands. They form an ecological variant of flora, as a historically-formed set of species growing on cultivated soils. For the rational use of the chemical and biological crop protection products and to produce safe and high-quality food, up-to-date data on the floristic diversity of weeds and the patterns of its geographical change are required. The need for a weeds' database arises that allows many specialists to work together independently. However, the great value of any database lies not in its existence, but in the accumulation of data that can be used to analyse the factors affecting the species diversity of weeds. A dataset of weed species diversity and their distribution in the European part of Russia, based on the results of the authors' own research from 1999 to 2019, has been created. The dataset includes 24,284 observations of occurrences of weed plants, which were obtained on the basis of 2,049 relevés of segetal plant communities in seven regions of the European part of Russia. In total, the dataset includes information about 329 species of vascular plants growing in 65 farmlands: cereals, spring and winter crops, industrial crops, row crops and perennial grasses (Tretyakova et al. 2020).