High seed production makes Sporobolus indicus var. pyramidalis a difficult to control invasive grassland plant. The objective of the present study was to investigate the bioactivity of Cyperus rotundus, Phyllanthus tenellus and Ricinus communis green leaf extracts and of Carica papaya seeds on S. indicus germination without breaking dormancy, simulating the field conditions. The ethanolic extract bioactivity of C. rotundus, P. tenellus, R. communis green leaves and C. papaya seeds, at concentrations of 25, 50 and 75% in S. indicus germination was evaluated. Carotenoids, flavonoids, soluble phenolic compounds and total tannins were quantified in the extracts. The chemical component concentrations varied between alcoholic extracts. The P. tenellus extracts at all dilutions and those of R. communis and C. papaya at 75% completely suppressed S. indicus seed germination at five and ten days which can be attributed to their high tannin concentration, total phenolic compounds and flavonoids.