The urgency of this research is determined by the interest in modern linguistics in revealing the specificity of the national worldview. The aim of the study is to investigate and analyze motivation of meaning and inner form of Russian phraseological units with a floral component. The article reports the results of the analyses of the phraseological units with a former lexeme – phytonym as one of their components. Phraseological units with a floral component are the units which incorporate a phytonym of a generic and common notion (teplichnoe rastenie, temnyy les, zatevat' syr-bor, puskat' korni, pristat' kak bannyy list, khot' trava ne rasti), as well as a component – name of some specific plant (osinovyy list, dubovaya golova, mak – makov tsvet, beleny ob"elsya, izrubit’ v kapustu). It is emphasized that the analysis of the formation of semantic structure of phraseological units with a floral component is of considerable importance since the plants play a big role in the life of a person; they form and translate symbolic, mythological and religious ideas. Special attention is paid to the identification of the regularities and the specificity of phraseogenetic potential of floral lexemes (phytonyms). The novelty of the study might be determined by the fact that the motivation of the inner form of phraseological units with a floral component has not been studied in detail so far. It has been revealed that the inner form is based both on the floral symbols universal for the human culture and on the physical properties of some specific plants people deal with in their daily life. The national markedness of phytonyms in phraseological units can manifest itself on the level of symbols and can become the basis of the patterns and stereotypes of human behavior. The results obtained make it possible to conclude that the discovery of the motivation of the semantics of phraseological units with a floral component plays a considerable part in the study of the mentality of a nation.