Field experiment on different sowing dates of two winter rapeseed cultivars (Brassica napus L. spp. and oleifera biennis Metzg.) was carried out in years 2009-2010 at the Experimental Station of the Aleksandras Stulginskis University (54°53’ N; 23°50’ E). The objective of the study was to evaluate the effect of winter rapeseed sowing date on the biometric parameters of rapeseed rosette: number of leaves, root collar diameter, height of apical bud, and its chemical composition: N:K ratio, amount of dry matter, total sugar in autumn before wintering, changes of chemical composition during the autumn- winter period, and overwintering. Sowing date significantly influenced all the examined indexes. According to the biometric parameters, the chemical composition of leaves, and the apical bud, winter rapeseed sown between August 30^th and September 5^th was best prepared for wintering and overwintered. Growth during the period of preparation for overwintering was more intensive. Changes in the chemical composition during the overwintering period were more favourable and the overwintering of winter rapeseed was better in the hybrid cultivar Kronos compared with cultivar Sunday.

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