Effects of Essential Oils of Lavandula x hybrida Rev, Foeniculum vulgare Mill and Thymus capitatus L. on the Germination and Radical Length of Triticum aestivum L., Hordeum vulgare L., Lolium rigidum L. and Phalaris brachystachys L.

Essential oils obtained from lavender (Lavandula x hybrida Rev.), sweet fennel (Foeniculum vulgare Mill) and thyme (Thymus capitatus L.) were tested in vitro for their allelopathic effect on germination and radical growth of two winter cereals, wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) and two important grass weed species of these crops, annual ryegrass (Lolium rigidum L.) and short spiked canarygrass (Phalaris brachystachys L.). Linalool (27.51 %) and linalyl acetate (37.21 %) were the main constituents of lavender oil, and anethole (82.06 %) and carvacrol (75.30 %) those of sweet fennel and thyme oil, respectively. The investigated essential oils showed almost no effect on crop's germination. However, they caused radical length inhibition, with more pronounced effects recorded by lavender oil, followed by sweet fennel and thyme essential oil. The germination of L. rigidum and P. brachystachys was also greatly inhibited by the lavender, then by sweet fennel and then by thyme essential oils. The radical length of both grass weeds were inhibited more by the essential oil of lavender, then by that of thyme, followed by that of sweet fennel. On the basis of overall phytotoxicity, phytotoxicity of essential oils was in the order of lavender > sweet fennel > thyme, however with different response between crop and weed species, with the latter being more susceptible. The results could be regarded as potential alternative-essential oil bearing plant based weed control means.