The aim of this study divides into 3 main subjects: I. Test the quality of Danish grown, wide ringed, knot free Norway spruce timber when used for joinery. II. a) Investigate if Norway spruce can be pruned without damaging the stem wood. b) Measure the time and width for complete occlusion after pruning. c) Measure the height up to the living crown in young Norway spruce stands. III. a) Make recommendation for the foresters about when and how to prune Norway spruce. b) Calculate the increase in price required for the pruned timber, to make pruning pay back. The main results are: Part I: The knot free, wide ringed Norway spruce are suitable for joinery and almost as good as good quality Scots pine. This is found for planing, moulding in longitudinal direction and drilling. Moulding of Norway spruce in transverse direction is a bit more difficult because of the wide rings, and it requires sharper tools than used in the tests. Cupboard doors are made of the wood. It have a very satisfactory result (part I, figure 6 and 7). Part II a): The pruning has caused damage to the stemwood in only a very few cases, and usually the damage is enclosed in the occlusion wood, and therefore makes no problems. b) In stands with a spacing commonly used in Denmark (3500-4500 trees/hectare) it is possible, for practical purposes, to use an average value of 2 cm for the width of complete occlusion. This means it takes 4 cm in diameter growth, after the pruning, before the knots are overgrown. In contrast to the occlusion width, the occlusion time is much affected by the site class; the lower the growth speed, the longer it takes to overgrow the stump. Therefore, pruning should be restricted to the best site classes. c) The mean height up to the living crown of young stands (stand height 7-9 meter) varies between 0,5 and 3 meter for stands planted with a spacing commonly used in Denmark (3500-4500 trees/hectare). Part III: a) The trees which are selected to be pruned should be (1) among the dominant or co- dominant trees, (2) be straight and (3) have a good distribution in the stand. There should be pruned the number of trees which are expected to stay until the end of rotation, and if desired, a bit more because it may be expected that some of the pruned trees will be cut in the early thinnings. To minimize the size of the defect core (knotty core the width of occlusion) and get a high clear bole, it is necessary to prune in 2 steps. The first pruning should be done just after the first thinning. Recommendation of when to prune (for site class 2 the pruning should be done 3-4 years later): (Table). If the recommendation is followed, 75-80% of the trees will get a defect core with a diameter less than 15 cm in breast height, and the increment will not be affected essentially. b) The extra price required for the pruned time is found by prolongation of the initial....
