This study was conducted to investigate the effect of Rumex acetosella (Red sorrel) shoot and root extracts treated with Festuca arundinacea (Tall fescue) and Trifolium repens (White clover). As a result of obtaining GR50 (Growth retardation 50%) by in vitro seed bioassay, the shoot extract GR50 was 1,409 mg L-1, root extract GR50 was 3,403 mg L-1 in F. arundinacea , and the shoot extract GR50 was 1,380 mg L-1, root extract GR50 was 1,902 mg L-1 in T. repens. As a result of treating the shoot extract and soil mixture on the soil surface, the germination rate of F. arundinacea was significantly reduced compared with the control when the shoot powder was more than 60%, and shoot length, root length, fresh weight, and dry weight showed the lowest values at 60%. And the germination rate, shoot length, root length, fresh weight, and dry weight of T. repens were significantly reduced compared with the control when the shoot powder was more than 20%. As a result of foliage treatment of shoot extract, F. arundinacea and T. repens showed a significant decrease in shoot length, fresh weight, and dry weight, chlorophyll content in the 100,000 mg L-1 treatment compared with the control.