The knowledge of plants interactions is used for their better protection and cultivation. Theaim of this study was to determine the influence of alcoholic extracts from the leaves of thecommon sunflower (Helianthus annuus) on selected physiological parameters of plants ofwhite mustard (Sinapis alba ‘Barka’). The seeds germination, the growth, the fresh and drymasses of plants grown from seeds and germinated on the sunflower extracts and plantswatered by H. annuus extracts during the growth phase were studied. In the growth phase, thefresh masses of all organs were increased on 5 % extract, however significantly decreasedon 10 % extract. The dry mass of S. alba was not significantly changed. In the germinationphase, much less changes of these parameters were revealed. In general, extracts... fromH. annuus leaves inhibited germination of S. alba seeds, but stimulated growth of plants incase of application of 5 % concentrations during the germination phase and inhibited theirgrowth in case of application of 10 % concentrations during the growth phase.