In vitro experiments were conducted to assess the inhibitory potential of root leachates (in methanol and ethanol) of selected weeds on germination and seedling growth of Santa Maria Feverfew plant (Parthenium hysterophorus L.). Based on the field survey the potential plants were selected and leachates were prepared at 50% and 100% concentration in both methanol and ethanol solvent. The results revealed that root leachates of C. occidentalis in ethanol solvent at higher concentration (100%), inhibits germination and seedling growth as compared to methanol solvent and was found to be significant (P<0.05).