The influence of nitrogen fertilisation on morphological traits of chosen white clover cultivars grown under competition with perennial ryegrass was examined. The experiment was carried out in controlled environment. It was found that the level of nitrogen fertilisation significantly affected the morphological traits of white clover that are closely related to the effectiveness of occupation and utilisation of the living space by white clover and to the ability of its regeneration. This way the level of nitrogen fertilisation affects the stability and productivity of white clover as well as interspecific competition with perennial ryegrass. It seems that the direction of the observed morphological changes is similar for the whole species, while the reaction-power is cultivar specific. The differences between examined cultivars suggest that the level of the nitrogen fertilisation should be fitted to the cultivar features. The results of the experiment show that the observation of the white clover morphological traits could be useful for the best selection of cultivars for the defined environmental conditions.