The allelopathic potential of different concentrations (0, 5 %, 10 %, 20 % and 40%) of Medicago sativa shoot extracts were assayed on germination and radicle growth of four weed species( Amaranthus hybridus, Amaranthus albus, Solanum nigrum and Chenopodium album) in a laboratory experiment as completely randomized factorial with 3 replications. The results showed that, final germination percentage, mean germination time, germination uniformity (GU), time to 10%, 50%, 90% germination and radicle length of all species were influenced by the extract concentration of M. sativa. weed species and their interaction. By increasing the aqueous extract concentrations, the final germination percentage decreased linearly and the mean germination time and time to 10 % and 50 % germination increased linearly. radicle length, GU and time to 90 % germination followed a second order regression and by increasing the water extract concentration the radicle length decreased and time to 90 % germination increased and the GU to the 20% concentration increased then decreased. S. nigrum had the greatest germination percentage radicle length and GU and Ch. album had the longest mean germination time and time to 10%, 50% and 90% germination. A. hybridus had the fewest germination percentage, mean germination time, radicle length, time to 10%, 50% and 90% germination and A. albus had the fewest germination uniformity. In total S. nigrum was the most resistant species and A. hybridus was the most susceptible species to water extract of M. sativa.