This study aimed to investigate the effect of delay in planting date on the traits of the rosette stage and various phenological stages of oilseed rape. For this purpose, an experiment was conducted in split plots based on a randomized complete block design with three replications at the Agricultural and Natural Resources Research Center of Hamedan Province Iran in 2012. The main factor was planting date in four levels, including 10 September, 20 September, 30 September, and 10 October. The second factor was four genotypes (Okapi cultivar, Tassilo, Octans-NK, and Elite hybrids). The results showed that the number of leaves per plant in the rosette stage was only affected by planting date. However, crown diameter, root length, root dry weight, and percentage of frost were affected by planting date, genotype, and their interactions. The studied genotypes in the first and fourth planting dates often did not differ in terms of seedling stage and rosette traits. Still, in the second and third dates, the genotypes' response was often different, and in general, the Octans-NK and Tassilo genotypes showed less susceptibility to planting. With the delay in sowing, the length of the emergence period increased in all genotypes, but the growing degree day required for this stage decreased, so the genotypes entered the rosette stage with weaker vigor. Almost all genotypes, regardless of planting time, emerged from the rosette simultaneously and went through the following stages with a slight difference, which caused a delay in planting time to significantly reduce the cumulative temperature and growth period length in all genotypes.
