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N fertilizer labelled with 15N was used to follow the accumulation and distribution of N applied at different times after planting Eucalyptus grandis W Hill ex Maiden seedlings in south-eastern Queensland, Australia. The first application was made to selected trees at 0.12 y after planting (T0), and treated trees were harvested at intervals after. Further labelled applications were made on different sets of trees 0.50, 0.74, 1.30 and 1.49 years after T0; T0.5, T0.74, T1.30 and T1.49 respectively. After 0.5 y there was no significant difference in growth between T0 trees and unfertilized controls, but after 1 y above-ground biomass and N content of the controls was only 30% and 39% of the fertilized trees respectively ( P <0.05). At later applications controls were not significantly different from fertilized trees up to 1 y later, but after 2 y above-ground biomass and N content was reduced ( P <0.05). Growth reductions occurred after leaves present on the tree at the time of fertilizer application were shed. Leaf biomass and N content increased steadily to age 1.5 y and then stabilized at about 2.5 kg tree-1 and 35 g tree−1 respectively, new growth balanced by litter fall. N content in woody material (stems+branches) increased steadily, equaling that of the leaves at 3.5 y. N derived from fertilizer and the proportion of applied N recovered peaked at 1 y and then decreased. These relationships were not affected by time of application. In T0 trees N in above-ground parts derived from fertilizer increased steadily to 42% of the total 0.5 y after application. It then decreased rapidly after leaf fall commenced while total N content increased. When observations ceased 3.5 y after planting, less than 5% of the N in the trees was derived from fertilizer. N uptake was two-phased. In the first year mineral N from the fertilizer was taken up by the trees. In subsequent years fertilizer contributed to the tree growth but the N taken up came from a different source. [ABSTRACT FROM AUTHOR]