University of Tabriz Journal of Plant Physiology and Breeding 2008-5168 16 1 2026 02 01 Yield and chemical constituents of Dragon’s head (Lallemantia iberica Fisch. et Mey) as influenced by planting date and spacing 41 53 21275 10.22034/jppb.2026.68945.1377 EN Vida Fattahi Department of Plant Production and Genetics, Faculty of Agriculture, Urmia University, Urmia, Iran. Alireza Pirzad Department of Plant Production and Genetics, Faculty of Agriculture, Urmia University, Urmia, Iran. Saeedeh Rahimzadeh Department of Plant Production and Genetics, Faculty of Agriculture, Urmia University, Urmia, Iran. Journal Article 2025 09 01 <strong>Objective:</strong> Agricultural strategic decisions, like planting dates and spacings, have direct impacts on sustainable crop production. This experiment aimed to investigate the effects of different planting dates and spacing on grain yield and chemical constituents of dragon’s head (<em>Lallemantia iberica</em> Fisch. et Mey).<br /><strong>Methods:</strong> A split-plot design based on a randomized complete block design with three replications was carried out to study the influence of planting dates (March 18, April 2, and April 18) and spacing (20×3, 20×5, and 30×2 cm inter- and intra-row spacing) on <em>L. iberica</em> at Urmia University, Iran, in 2018. Seeds of dragon's head were provided by the Agricultural Research, Education, and Extension Organization, Urmia, Iran. Seeds were sown on three specified planting dates by hand at a depth of 2 cm in plots of 150×200 cm. Then, they were covered with a thin layer of soil.<br /><strong>Results:</strong> The maximum grain yield (520 kg/ha), grain oil percentage (31.84%), and grain oil yield (165 kg/ha) were obtained from the March 18 planting date with 30×2 cm spacing. Also, the highest biomass (3796 kg/ha), essential oil percentage and yield (0.34% and 13.17 kg/ha, respectively), mucilage percentage and yield (15.30% and 70 kg/ha, respectively) were observed on the March 18 planting date. The maximum percentage of grain nutrients (NPK) was obtained from the earliest planting date and the planting spacing of 20×5 cm. The highest percentage of total unsaturated fatty acids against the lowest saturated fatty acids (stearic and palmitic acid) belonged to March 18. However, the highest percentage of some of the important compounds in the <em>L.</em> <em>iberica</em> essential oil, including thymol, caryophyllene oxide, and phytol, was obtained on April 18.<br /><strong>Conclusion:</strong> Early planting on March 18 was a better date for <em>L. iberica,</em> which gave a higher grain yield than other planting dates. Mutually, late sowing reduced the nutrient uptake, biomass, and some quality traits. Also, spacing of 30×2 cm with lower plant density showed better results in terms of plant quality. https://breeding.tabrizu.ac.ir/article_21275_378f4d8cda7a1d7a31ad57b734159df2.pdf