Environmental pollution is serious problem all around the world. Over the past decades, several well-known heavy metals have received much attention of researchers, and new information has been collected on their toxicity. However, knowledge of environmental chemistry of many other potentially toxic trace elements is scarce, though it is known that an increase of concentration of any element in soil can lead to negative consequences for plants. Nowadays the basic challenge is to examine the biogeochemistry of the trace elements we know almost nothing about. In our research, we performed a field experiment with two plant species couch grass: (Elytrigia repens (L.) Desv. ex Nevski) and dandelion (Taraxacum officinale (L.) Weber ex F.H. Wigg). The plants belong to different botanical taxa. Couch grass and dandelion were grown in soil spiked with RbCl. The concentrations of 23 macro- and trace elements in the plants were determined by ICP-MS. Raman spectroscopy was used for analysis of organic compounds. Although couch grass and dandelion were grown in the same site and collected simultaneously, the concentrations of many elements in the plants differed significantly, and more differences were found between concentrations of elements in leaves of the two plant species. Both plants were capable of accumulating large amounts of Rb. The bioaccumulation of Rb resulted in statistically significant variations in the concentrations of several elements in roots and leaves of the plants. There were marked changes in anthocyanins in dandelion resulted from its growth in the Rb-contaminated soil. On the other hand, no such effect was observed for couch grass.