In order to evaluate the effect of irrigation regimes and sowing dates on linolenic acid (Omega-۳) content in dragon's head (Lallemantia iberica), an experiment was conducted factorial as a randomized complete block design in three replications in the research farm of Shahed University on crop year ۲۰۲۱–۲۰۲۲ in the research farm of Shahed University. The experimental treatments included: Irrigation regimes at three levels: I۲۰: Irrigation after ۲۰% depletion of soil available water (SAW); I۴۰: An irrigation after ۴۰% depletion of SAW; and IS۲۰: Irrigation at sowing and before flowering based on ۲۰% depletion of SAW. The second factor was the sowing dates of autumn (November ۱۵) and spring (March ۱۵). The interaction effect of autumn sowing date and irrigation regime I۲۰ produced the greatest seed yield (۶۸۰,۱ kg.ha-۱), harvest index (۰,۲۸), chlorophyll b content (۰.۴۵۷ mg.g-۱ Fw), seed number per plant (۴۶۹,۰), and branch number per plant (۹.۸۳). Also, the amount of linolenic acid was greater under the treatment of sowing date and irrigation regime I۲۰, with values of ۶۴.۰۷% and ۶۴.۳۳%, respectively. A water shortage in the soil also decreased linolenic acid content under deficit irrigation treatments (IS۲۰ and I۴۰) although in I۴۰ it was not statistically different from I۲۰. Totally, it was clearly determined that the low temperature of autumn increased Omega-۳ in the Dragon's head.
