Bioassays were performed to study the allelopathic effect of dried leaf powder of Carica papaya, Parthenium hysterophorus, Euphorbia helioscopia and Rumex dentatus on intact and pre-germinated seeds of R. dentatus, Avena fatua, Helianthus annuus (K.S.E 7777), Zea mays (Islamabad Gold 2010) and Triticum aestivum (Wafaq 2001). Experiments were designed in CRD with five replications accounting parameters of germination percentage, radicle length (cm) and plumule length (cm). C. papaya and P. hysterophorus decreased the emergence of R. dentatus and A. fatua on agar similarly; all treatments inhibited the germination of R. dentatus and A. fatua. In direct seeding, radicle growth of R. dentatus and A. fatua was decreased by all treatments. In same experiments, plumule of A. fatua was significantly repressed by E. helioscopia treatments. In direct seeding, E. Helioscopia reduced the radicle length of R. dentatus and A. fatua. R. dentatus radicle growth was also significantly inhibited by P. hysterophorus. All treatments inhibited the plumule length of R. dentatus and A. fatua. P. hysterophorus significantly inhibited radicle as well as the plumule of all test species. P. hysterophorus and E. helioscopia treatments were evaluated as good weed suppressants.  Weed suppressive effects of these treatments are attributed to their secondary metabolites needed to be explored. It is recommended to conduct experiments for weedicidal potential of the species in field to assess the efficacy of leaf dried powder along dose requirements in natural agriculture systems.