Plants, as well as their residues (mulches), release physiologically active substances (allelochemicals), which may affect plant germination, development, and productivity. In this study we investigated the allelopathic effects of aqueous extracts of organic mulches (winter wheat straw, peat, sawdust, and gramineous grass) at different concentrations on germination and early growth of radish (Raphanus sativus L.), carrot (Daucus sativus Röhl.), and lettuce (Lactuca sativa L.). It was found, that the strongest negative effect on the germination and shoot and root development of investigated vegetables was with the highest concentration (1 : 10) of the grass aqueous extract. Peat mulch aqueous extracts had the least negative impact on all vegetable seed germination. Straw and peat mulches stimulated the early growth of R. sativus shoots, but there was a negative affect on D. sativus shoot development. The aqueous extracts of various organic mulches had negative effects on R. sativus, while mostly positive effects found on L. sativa root development.