The conducted experiment was aimed at determining the effect of aqueous extracts from dry roots and shoots of common weed nipplewort (Lapsana communis L. subsp. communis) on seeds germination and early growth of radish (Raphanus sativus L. var. radicula Pers.), cultivars ‘Rowa’, ‘Krakowianka’, ‘Półdługa’. The experiment was carried out in the form of Petri dishes tests with 3 different percentage concentrations of extracts (1%, 3% and 5%, respectively). The germination indexes used here revealed that the germination capacity of the radish seeds was significantly inhibited by extracts from the roots and shoots of L. communis subsp. communis. The elongation growth of radish roots and hypocotyls was stimulated to a higher percentage by extracts from nipplewort roots than by extracts from shoots. The fresh and dry mass of the radish seedlings depended on the type (roots/shoots) and concentration of the extract as well as the radish cultivar. The electrolyte leakage was the highest in seedlings watered with 5% extract of nipplewort shoots. The cultivar most sensitive to nipplewort extracts turned out to be ‘Półdługa’, and the least sensitive was ‘Rowa’. The response of radish seeds to nipplewort extracts is probably due to the presence of allelochemical compounds and their synergistic interaction.