Bidens frondosa is an invasive xenophyte which is naturalized in vegetative communities on the territory of the Southeast of Europe. The natural area of B. frondosa is in the North America. The secondary one is on the territory of Eurasia, here B. frondosa forces out native B. tripartita that is explained by competitive superiority of the North American species on growth rates and seed efficiency on soils of different fertility and water regime. In the secondary area in Eurasia B. frondosa grows on banks of reservoirs and water currents as well as on other damp habitats (including disturbed ones) often in large quantities. This species is also found on saline soils of the European Southeast. It is registered in communities of association Atriplici aucheri-Tamaricetum ramosissimae Golub et al. 1998 belonging to class Nerio-Tamaricetea Br.-Bl. et Bols 1958 order Tamaricetalia ramosissimae Golub in Barmin 2001 alliance Elytrigio repentis-Tamaricion ramosissimae Golub in Barmin 2001, in one of its subassociations A.au.-T.r. althaeetosum Golub et al. 1998, but there B. frondosa is the diagnostic taxon as well as the constant species that is met in all of its described coenosis.