The most common form of the Brassica napus L. is oilseed rape. Because of its physical characteristics the seed is very mobile and therefore disposed to spillage. Uncontrolled seed loss represents the potential for the appearance of volunteer and feral populations of B. napus inside and outside production areas; B. napus seed remains viable in the soil for several years. The appearance dynamics of these plants is dependent on the soil seed bank potential and complex interactive characteristics of the genotype seeds and soil and agro-climatic factors. The presence of undefined pollinating resources originated from soil seed bank in the nature presents the potential for spontaneous intra- and inter-species pollination of B. napus reflected also in its genetic structure.