In in vivo experiments the natural biologically active substances, which may reduce the application of chemical plant protection pesticides were examined. As dressing preparations water extracts (macerations, infusions) prepared from various parts of 39 plant species were used. For dressing non-disinfected seeds of two varieties of oat: Akt with naked seeds and Bajka with chaffed seeds were used. The experiment was conducted as a filter paper test, germination viability (I date) and germination capacity (II date) as well as healthiness of the seeds were determined. A significant differentiation of the effect of the extracts depending on extracts’ origin (plant), mode of their preparation and of interaction between these factors was revealed.