Delayed sowing of winter oilseed rape in Poland affects plant growth and seed yield. A study compared optimal and delayed sowing dates and two cultivars. Delayed sowing shortened plant growth but did not change seed yield. Optimal sowing increased plant density, while delayed sowing increased seeds per silique. Cultivar Arsenal F1 had higher seed yield than Monolit. Delayed sowing increased fibre and zinc in seeds, but decreased protein, phosphorus, and potassium.