Parthenium hysterophorus L. is one of the fastest growing weed. It belongs to family Asteraceae. Parthenin is reported as a principle component of this plant and is responsible for allelopathy. Every year due to its luxuriant growth in the crop fields, as a weed it leads to destruction of thousand tons of crops around the globe. In the present study allelopathic effect of root extract (2%, 6% and 10%) of P. hysterophorus on percent seed germination of 9 selected crops (Brassica juncea, B. nigra, Coriandrum sativum, Baby corn, F1 hybrid beet, F1 long radish, fenugreek, Japanese white radish), on its own seeds and its effects on the soil (control soil (garden soil), rhizosphere soil of Parthenium and leachet soil) was studied. After eight days of incubation at room temperature, it was found that among the nine plants Coriander Local Variety was most affected with zero percent seed germination with 2, 6 and 10% of the root extract. Maximum percent of seed germination (80±10) was recorded with F1 Hybrid Beet at 2%. Parthenium root extract was found auto toxic to its own seeds at 6 and 8% respectively. After 10 days of treatment, increment of pH from control soil (pH: 7.10) to rhizosphere soil of the Parthenium (pH: 7.28) was reported. Organic carbon, potassium and Nitrogen also follow the same trend whereas the EC (0.49%) and P (13Kg/hacters) were found maximum in root leachet soil.