Cilj istraživanja bio je utvrditi alelopatski potencijal lucerne (Medicago sativa L.) na klijavost sjemena i rast klijanaca rotkvice (Raphanus sativus L.), radiča (Cichorium intybus L. var. foliosum) i rajčice (Lycopersicon esculentum Mill.). Vodeni ekstrakti pripremljeni od suhe nadzemne mase lucerne u tri koncentracije (1 %, 2,5 % i 5 %) testirani su u laboratorijskim uvjetima. Alelopatski potencijal lucerne ovisio je o test vrsti, koncentraciji vodenog ekstrakta te mjerenom parametru. Najslabije djelovanje zabilježeno je na klijavost te rast klijanaca rajčice. Povećanjem koncentracije vodenog ekstrakta povećavao se i negativni alelopatski potencijal. Najmanji utjecaj vodenih ekstrakata zabilježen je na suhu masu klijanaca test vrsta. The aim of the study was to determine the allelopathic potential of alfalfa (Medicago sativa L.) on seed germination and seedling growth of radish (Raphanus sativus L.), radicchio (Cichorium intybus L. var. foliosum) and tomato (Lycopersicon esculentum Mill.). Water extracts prepared from dry alfalfa biomass in three concentrations (1%, 2.5% and 5%) were tested under laboratory conditions. The allelopathic potential of alfalfa depended on the test species, the water extract concentration, and the measured parameter. The weakest effect was recorded on germination and growth of tomato seedlings. As the concentration of the water extract increased, the negative allelopathic potential also increased. Dry weight of seedlings of test species was the least affected.