A study was carried out to find distinctions in the nitrogen status of plants of two forms of the birch species Betula pendula early in the ontogeny, and to compare their responses to nitrogen application to the soil. Compared to silver birch, curly birch had higher nitrogen supply to the organs, higher concentrations of the main transport nitrogen compound – amino acid citrulline – in the trunk, and the concentration of glutamic acid – a central link in nitrogen metabolism – in the leaves is maintained at a certain level during the growing season. Application of nitrogen fertilizers to the soil resulted in a notable rise in the content of protein nitrogen in the bark and wood of 3-year-old curly birch saplings during intensive cambial activity (July). High dose nitrogen treatments significantly enlarged the amount of amino acids in the leaves and, especially, in the bark of curly birch. Curly birch saplings responded to a moderate dose nitrogen treatment with weight increment, when the whole plant weight increased by 42 %, and the weight of axial organs – by 57 % compared to the control.