Vegetation cover trends of meadow-steppe plots of the Kyiv Plateau are summarized in the context of the protection of such plots in situ and ex situ. It was found that the vegetation cover trends of the natural meadow-steppe plots of the Kyiv Plateau, located on protected and promising for reserved territories, and the artificially simulated meadow-steppe phytocoenosis on the plot «Steppes of Ukraine» of the M.M. Gryshko National Botanical Garden of the NАS of Ukraine are similar. Mesophytization and phytoinvasion of such aggressive alien plant species as Asclepias syriaca, Robinia pseudoacacia, Solidago canadensis are observed in meadow-steppe plots, both in situ and ex situ. Cenopopulations of rare plant species can remain stable in meadow-steppe plots with minor mesophytization and adventitization.