Winter wheat harvests shows large variations over the years, and for the optimal plant population in the spring sowing time, stand establishment and winter survival is crucial. We want to examine the relation between sowing time, seed rate and temperature, and how it affects winter wheat crop development in two different modern types of varieties of winter wheat. Type 1, Brons is a variety that produces many side-shoots and many kernels while variety 2, Julius, produces harvest by a moderate kernel density but with a high grain weight. The interaction between sowing time and seed rate is examined in two field trials, one in Skåne and one in Uppland. Four sowing times and five seed rates (100 to 500 grains m2) are compared for three years. Temperature is recorded in the experimental fields to investigate the impact of climate on crop development. Winter survival, and the phenological development stages are documented, yield and quality are measured.