To study the effect of farmyard manure and plant growth regulators on yield and essential oils of dragonhead, an outdoor experiment was conducted in Maragheh, Iran. The experiment was carried out based on randomized complete block design with three replications. Three amounts of farmyard manure (FYM) including 0, 10 and 20 t/ha together with foliar growth regulators including 0, salicylic acid (SA), ascorbic acid (ASc) and SA + ASc were used. The results revealed that application of 10 and 20 t/ha farmyard manure significantly increased plant height and the number of lateral stems. However, application of 20 t/ha led to the increase of the number of the main and flowering stems, biomass and essential oil percentage of dragonhead compared to control. The effect of growth regulators on the number of lateral and flowering stems, and biomass was significant: foliar application of SA and ASc separately or in combination increased the number of lateral stems; however, the number of flowering stems and biomass of dragonhead increased only when both growth regulators were used in combination (SA + ASc). The results also indicated that the highest length of inflorescence (13.57 cm) and essential oil yield (41.83 kg/ha), by 31.4 and 126.3% increment, respectively, were observed under foliar application of 20 t/ha farmyard manure together with SA + ASc application compared to the control
