To examine the minimum levels of nitrogen concentration in leaves at harvest time needed for high-quality cut-flower stock, 'Asanami,' the effects of nitrogen treatments on the concentrations of phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the leaves and stem (experiment 1), and the influence of the period of nitrogen (N) supply on growth and cut-flower quality (experiment 2) were observed. We designed two kinds of experiments in which plants were grown by the use of sand cultures supplied with 130-200 mL of nutrient solution daily. The first experiment was designed to use a nutrient solution containing 10, 20, 40, 60, 100 and 180 g kg^<-1> N. The second experiment was designed to use a nutrient solution without nitrogen on days 17, 25, 32, 39, 45, 51 and 60 after transplanting, in contrast to a normal solution, which contained 100 g kg^<-1> N. The minimum level of nitrogen concentration that resulted in good cut-flower quality was about 30-32 g kg^<-1> in leaves at the upper 11th position. This level was sufficient for nitrogen absorption to continue until visible flower bud or the beginning of flowering. There was a high positive correlation between N concentration and K (stem only), Ca (except 180 N), P and Mg concentrations in the leaves and stem, respectively, but K concentration in the leaves decreased when N increased over 40 g kg^<-1> N.