Tricolorin A acts as pre- and post-emergence plant growth inhibitor. In pre-emergence it displays broad-spectrum weed control, inhibiting germination of both monocotyledonous (Lolium mutliflorum and Triticum vulgare) and dicotyledonous (Physalis ixocarpa and Trifolium alexandrinum) seeds, being the dicotyledonous seeds the most inhibited. Tricolorin A also inhibited seedling growth, and seed respiration, and since the concentrations required for inhibiting both germination and respiration were similar, we suggest that respiration is one of its targets. Tricolorin A at 60 µM acts as a post- emergence plant growth inhibitor by reducing dry plant biomass by 62%, 37%, 33%, and 22% for L. multiflorum, T. alexandrinum, T. vulgare, and P. ixocarpa, respectively, 18 days after its application. In order to determine the potency of tricolorin A as a plant growth inhibitor, paraquat was used as control; the results indicate that tricolorin A acts as a non-selective post-emergence plant growth inhibitor similar to paraquat, since both reduced the biomass production in P. ixocarpa and T. alexandrinum. Therefore, we suggest that tricolorin A will be a good biodegradable herbicide for weeds.