Any different strategies used by higher plants to win the life competition, always involve chemical interactions between organisms. Allelochemicals are standard chemical weapons not only in the case of toxic plants; they are also present in common vegetables such as carrot. Numerous chemical compounds synthesised in carrot tissues, such as asarones, chlorogenic acid, trans-2-nonenal, and sesquiterpenes show allelopatic activity. Asarones are synthesised in carrot leaves and stems in varying quantity during the growth season. There are known examples of nemathocidal and herbicidal activity of these compounds. These phenylpropanoids also have a moderate influence on the insects behaviour. The results of in vitro studies showed fungicidal activity of asarones against several species of phytopathogenic fungi. Chlorogenic acid and trans-2-nonenal isolated from carrot roots show insecticidal activity against carrot fly (Psila rosae Fabr.) larvae. Carrot seed oil and its main sesquiterpen components as carotol, caryophyllen and caryophyllen oxide, exhibited herbicidal or fungicidal activity.