Jatropha curcas J. curcas J. curcas J. curcas Parthenium hysterophorus J. curcas P. hysterophorus L. ( ) is gaining interest as biodiesel plant in Pakistan. Therefore, it is necessary to investigate the interaction of not only with crop plants but also with weed species before its introduction into agroforestry systems. During present investigation, allelopathic potential of leaf aqueous extract was investigated on seed germination and seedling development of L. Extracts were applied at 25%, 20%, 15%, 10% and 5% as seed soaking for 8 hours prior to sowing. Phenolics compounds were found in aqueous extracts and were higher in 25% extract (52.72 mg gallic acid eq. / gm of extract). Higher concentration of the extract (25%) significantly decreased seed germination (%), seed germination index, shoot fresh weight, shoot dry weight, root length, root fresh weight, root dry weight, seedling relative water content and seed vigor index. It was inferred from findings of the present investigation that aqueous extract of exhibits inhibitory effects on growth and development of and therefore could be a potential source of botanical herbicide in the control of this noxious weed species.