Secondary compounds in higher plants have great diversity in terms of biologic activity. Most of them are used for the defense by plants. This study aims to investigate the effects of benzoic acid, salicylic acid, and Persica vulgaris Mill. (Peach) on the germination of the seeds of cultivated plants such as Triticum aestivum L. (wheat), Zeamays L. (corn), Cicer arietinum L. (chickpea), as well as weeds such as Lepidium campestre (L.) R. Br. and Convolvulus arvensis L. Method 1, in which benzoic acid, salicylic acid, and Persica vulgaris Mill. are added to the germination environment at different doses, and Method 2, in which they are mixed with the irrigation water at the specified doses, have been employed in this study. As a result of this study, it has been determined that the leaf extract of P. vulgaris Mill., Benzoic acid, and salicylic acid prevent the growth of the root and stem in all seeds at high doses in both methods, and they increase the growth at low doses. According to the GC-MS results of the leaf extract of P. vulgaris Mill., benzoic acid has been determined to be at the highest rate. No difference has been found between months as a result of the HPLC analysis of the amounts of benzoic acid. The determination of negative effects of benzoic acid, salicylic acid, and peach leaf extract both on cultivated plants and weeds at high doses will repress the development of cultivated plants as well as weeds. Growing cultivated plants in places with peach trees may decrease the yield. The leaves should not be let decompose on the soil in defoliation season, and fallen leaves should be collected. Not collecting all of the leaves and leaving some of them may increase the development of weeds in the surrounding area since it may cause a low dose effect. (C) 2016 SAAB. Published by Elsevier B.V. All rights reserved.