Accepted in Journal of Horticulture Science 1 ˺ Effects of Organic and Chemical Fertilizers on Leaf Yield, Essential Oil Content and ˻ Composition of Lemon Verbena (Lippia citriodora Kunth) ˼ ˽ Ebadi, M.T a ., Azizi, M b ., Sefidkon, F c ., Ahmadi, N a* ˾ ˿   a Department of Horticultural Sciences, Faculty of Agriculture, Tarbiat Modares University, Tehran,  Iran. ˺˹ b Department of Horticultural Sciences, Faculty of Agriculture, Ferdowsi University of Mashhad, ˺˺ Mashhad, Iran. ˺˻ c Research Institute of Forests and Rangelands, Tehran, Iran ˺˼ ˺˽ ˺˾ * Corresponding author. Tel.: +98 21 48292088; fax: +98 21 48292200. ˺˿ E-mail address: ahmadin@modares.ac.ir (N. Ahmadi). ˺ ˺ ˺ Abstract ˻˹ Due to increasing demand to medicinal plants in the growing market of herbal medicine ˻˺ products, organic production and quality of raw material should be first aim for development ˻˻ of these products. In this regard, a pot experiment based on completely randomized design ˻˼ with six treatments and three replications on Lemon verbena carried out in experimental ˻˽ greenhouse of department of horticulture, Tarbiat Modares University during 2012. ˻˾ Treatments consisted of using vermicompost in 10, 20 and 30 %, vermiwash, complete ˻˿ fertilizer and control (without fertilizer). In the beginning of flowering, the leaves harvested ˻ and the essential oil extracted, then they analyzed by GC and GC/MS. The results showed that ˻ the maximum amount of leaf yield (7.73 g) and essential oil (1.1 %) was in using of 30 % ˻ vermicompost in the pots and the lowest (4.75 g and 0.8 %) belonged to the control treatment. ˼˹ The highest amount of citral (54.9 %) obtained from the complete fertilizer treatment but the ˼˺ maximum amount of limonene and 1,8- cineol (respectively 7.4 and 8.8 %) determined in the ˼˻ treatment of using 30 % vermicompost in the pot. In survey of the groups of essential oil ˼˼ components, the maximum amount of Monoterpene hydrocarbons and Oxygenated ˼˽ monoterpenes (respectively 12.4 and 63.3 %) belonged to using 30 % vermicompost in the ˼˾ pot. According to the results, it seems that application of vermicompost is an ideal alternative ˼˿ for chemical fertilizers in organic farming of Lemon verbena with high quantity and quality of ˼ active substances. ˼ Keywords: citral, essential oil, Lippia citriodora Kunth, vermicompost, vermiwash ˼ ˽˹ ˽˺ ˽˻ ˽˼ ˽˽