The effect of zinc sulfate (0.1 - 50 mg / l) on seed germination and initial stages of development of seedlings of three species of the genus Bidens L. Solutions of zinc sulfate throughout the indicated range of concentrations had no significant effect on laboratory germination of B. tripartita L. At 50 mg / L decreased the laboratory germination B. cernua L. and B. frondosa L. The toxic effect of zinc manifested in the growth and development of root systems of seedlings of all kinds: in B. cernua and B. frondosa at a concentration of 50 mg / l of the main root was absent in B. tripartita significantly decreased in length. Aboveground part of seedlings less responsive to the action of high concentrations of zinc in the medium. In terms of resistance to the action of zinc sulfate species are studied in the following descending series: B. tripartita> B. frondosa> B. cernua.