The effect of PK fertilization on the stem characteristics of pole stage Sitka spruce (Picea s;Ltchensis (Bong.) Carr.) was examined in this study.Ring width measurements were taken on cross-sectional cuts from each mid-internodal position, up to an over bark diameter of 7cm, for 40 control and 40 fertilised trees, and were used for the examination of the internal pattern of growth of the trees. Using the plotting facilities of the computer tree diagrams were constructed showing the different stages of the development of the trees. Following fertilization ring width and/or ring area increased dramatically over the stem of the fertilized trees, indicating possible changes in the stem form. The effect of fertilization was reflected clearly in the radial ring sequences, the longitudinal ring sequences and the sequences of rings parallel to the pith, as well as in the "contour diagrams" which were developed in particular for this study.