Two experiments were conducted with containerized `Hamlin' orange trees (Citrus sinensis [L.] Osb.) on `Swingle' citrumelo (C. paradisi Macf. × Poncirus trifoliata [L.] Raf.) rootstock to study the effects of N rate on growth of plants in the nursery. Treatments consisted of the following N rates: 12, 50, 100 and 200 mg·liter-1 applied once a week through drip irrigation. In Expt. 1, fertilization at the 200 mg·liter-1 rate resulted in greater scion growth, trunk diameter and total leaf dry weight as compared to the other rates. In Expt. 2, application of 100 and 200 mg·liter-1 rates resulted in greater scion growth and trunk diameter as compared to lower rates, but no differences were seen between the two highest rates. Trees receiving the 12 and 50 mg·liter-1 rates were stunted and leaves were chlorotic. Therefore, the optimum N rate for trees on `Swingle' citrumelo rootstock is between 100 and 200 mg·liter-1, although the 200 mg·liter-1 rate may not be economically justified. Moreover, the N rate for nursery plants growing on `Swingle' citrumelo rootstock in commercial medium may be higher than for other rootstocks, where rates less than 50 mg·liter-1 produce optimum growth.