The paper presents result of geobotanical survey of the southern part of Perm Region and northern regions of the Republic of Bashkortostan are presented; the distribution of Heracleum sosnowskyi Manden. in segetal (weed-field) communities is revealed. In the syntaxonomic space, the communities were classified in the association Conio maculatum – Stachietum palustris Khasanova et al 2018. New localities of the species in cultivated fields of Tatyshlinski district of the Republic of Bashkortostan were revealed. It has been established that Heracleum sosnowskyi infiltrates into the communities of grain crops – wheat, oats, barley and rye.

The paper analyzes alien component of the cenoflora of wheat crops surveyed in 2019–2022 in the Penza region. 42 adventive species were revealed, which is 25.9% of the total number of weeds in wheat fields. The leading families in terms of the species number are Asteraceae (10 species), Brassicaceae (9), Poaceae (7). As far as the immigration ways are concerned, xenophytes predominate (40), according to naturalization degree epecophytes prevail (38). More than half of the introduced species are archaeophytes (23) of Mediterranean and Iranian-Turanian origin. Plants of North American origin make up 47 % of the neophytes. The spectrum of life forms of adventive plants is dominated by herbaceous annual and biennial plants (88.1 %), indicative of the specific environments of this agrocenosis type. Tripleurospermum inodorum (L.) Sch. Bip. is the most widespread alien species in wheat crops of the Penza region. Investigation of wheat fields have resulted in registering of two quarantine objects of North American origin, namely Cuscuta campestris Yunck. and Ambrosia trifida L.

The herbarium of the Institute of General and Experimental Biology of the Siberian Branch of the Russian Academy of Sciences (UUH) (Ulan-Ude) represents 48.6% of the total number of invasive and potentially invasive species of Siberia and is represented by 72 species from 61 genera and 28 families (433 sheets). The leading family groups in the spectrum are Asteraceae (18 species), Brassicaceae, Fabaceae (8 species each), Poaceae (6 species), and Rosaceae (4 species). According to the invasive status, the herbarium contains 6 transforming species (Acer negundo L., Echinocystis lobata (Michx.) Torr. et A. Gray, Elodea canadensis Michx., Hordeum jubatum L., Medicago ×varia Martyn, Melilotus albus Medikus) and 5 potentially invasive species (Cuscuta europaea L., Elymus trachycaulus (Link) Gould et Shinners, Hesperis pycnotricha Borbrs et Degen, Solidago gigantea Aiton, Symphytum caucasicum M. Bieb.). The geography, ecology and chronology of the presented plants are considered.

The invasion of Berberis vulgaris L. into forest phytocenoses of the Voronezh Nature Reserve occurred as a result of the species cultivation at forest guard cordons and in tree nurseries of the protected area. The barberry naturalization in Pineta nemoralo-pratoherbosa was initiated by a fire in 1997. Currently, the species has become a structural component of the undergrowth in several forest areas. The state of the population indicates a high probability of an increase in the number and density of individuals in the near future, as well as further expansion of the species. In a number of reserves of the Russian Federation, the naturalization of alien plant species poses a real threat to biological diversity and natural changes. The effective functioning of Russian federal protected areas should include not only monitoring and study of biological invasions, but also practical measures to manage these processes (preventing and eliminating the consequences).

The paper presents data on the findings of 18 alien species in the city of Lugansk. Based on our own photographs available from Plantarium and iNaturalist websites, 12 species of adventive plants are recorded for the first time for the flora of Donbass, and 6 ones for the flora of the Lugansk People’s Republic. Information is given on locations, nature of habitats and abundancy of identified populations of alien plants, an approximate assessment of the degree of their naturalization and invasive potential being given. According to the degree of naturalization, most of them are epecophytes (eight species), five are colonophytes, three are phanerophytes and two are agriophytes. The results obtained are useful for compiling regional floristic reports and research on the species composition, distribution, and dynamics of adventive species.

The influence of Sosnowsky’s hogweed (Heracleum sosnowskyi Manden.) on the parameters of soil biological activity was studied in comparison with other types of plant communities (grass-forb meadow, small-leaved young growth) forming postagrogenic ecosystems in the middle taiga subzone of the Komi Republic. It is shown that H. sosnowskyi, when introduced into fallow lands, forms unique speciespoor plant communities preserved and self-sustainable for a long time. The soil biological activity in postagrogenic ecosystems is primarily influenced by the type of plant community (qualitative composition of plants) and the characteristics of the physic and chemical soil characteristics. Invasion of H. sosnowskyi into postagrogenic ecosystems of the middle taiga contributes to the activation of the vital activity of microbial communities, which is reflected in an increase in the value of microbial biomass compared to fallow lands occupied by grass-forb meadows and tree communities.

The reproductive characteristics and invasive potential of Pseudotsuga menziesii (Mirb.) Franco and its forms in the Volgograd region have been objects to our research. Our study has shown that, in terms of its ability to spread spontaneously, P. menziesii belongs to the species that spread vegetatively or by self-seeding alone, and therefore cannot be considered an invasive species. Representatives of the genus Pseudotsuga Carr. are used in forest reclamation to fix and afforestate sands and washouts and in greenery plantings in the Lower Volga region, but have not become widespread as forest-forming species. The use of P. menziesii and its forms in protective afforestation and landscaping as fast-growing, highly decorative, long-lived trees can be aimed at solving the urgent problem of forest reclamation in degraded areas.

The place of the term «xenophyte» in the system of alien (аdventive) plants is discussed. Attention is drawn to the use of this term by botanists in three different meanings: 1) referring to unintentionally introduced plants; 2) to denominate plants introduced into the study area from other areas not having direct contacts with it; 3) to indicate pants, introduced into the study area from both remote and contact geographical areas. It is shown that the third point of view seems to be more correct. Taken into account in an expanded interpretation, this term is more relevant than any other referring to alien plants. To name a group of unintentionally introduced plants, the term «aboiletophyte» can be recommended.

Among herbaceous ergasiophygophytes of the Donetsk Botanical Garden, 21 species show high adaptive potential and are classified by us as potential dangerous invasive ones. Petrosedum reflexum (L.) Grulich, Solidago canadensis L., Arrhenaterum elatius (L.) J. Presl & C. Presl are of the greatest danger as they are likely to have «transformer» status soon, if not regulated in their distribution. The species confinement with habitats types according to their degree of naturalness, type of maintenance, luminance and development of soil cover was analyzed.

According to the Convention on Biological Diversity, it is necessary not only to protect the native flora, but also to prevent the settlement of alien species. This is especially important for specially protected natural areas. The Polistovo-Lovat bog system, the largest in the European part of Russia, is protected by two reserves – Polistovsky in the Pskov region and Rdeisky in Novgorod. The author of the article has been monitoring the introduction of alien species in both territories for more than 20 years. By now three species of invasive plants have been noted in the Polistovsky Reserve: Impatiens glandulifera Royle, Epilobium adenocaulon Hausskn., Erigeron canadensis Michx., and 12 species in the territory of its protected area. Amelanchier spicata (Lam.) C. Koch, E. adenocaulon were recorded in the territory of the Rdeisky reserve and 4 species – in its protected area. The most widely distributed are I. glandulifera, E. adenocaulon, E. canadensis. Heraculum sosnowskyi Manden. grows near protected areas.