SUMMARY

Second-growth Douglas fir (Pseudotsuga taxifolia Brit t.) grown on a short rotation of up to 140 years wil l produce l i t t le, i f any, c lear wood. If c l ea r wood is desired, for example in the manufacture of ply-wood, then the young stands must be pruned. Several pruning experi-men t s a r e desc r ibed. In a 20-year-old stand, pruning w a s carr ied out to varying heights to determine the effect of the t reatments on subsequent t ree growth. It was found that up to half tree-height can safely be pruned without any adverse effect on tree growth. In another 20-year-old stand, pruning up to 14 feet, using a hand-saw and ladder, took an average of 7.62 minutes per t ree based on the time spent on 159 t r ees. A t age 36 yea r s t hese t r ee s were p runed to 3 4 feet. A plantation of Douglas fir was pruned to 20 feet. Pruning was carried out in three ways: 1. In three operations; 0 to 7 fee t; four years la te r, 7 to 1 3 feet; and another four years la ter, 1 3 to 20 feet. 2. In two operations; 0 to 1 3 feet; and four years la ter, 1 3 to 20 feet. 3. In one operation; 0 to 20 feet. It was found that pruning to 20 feet in one operation is the cheap-est method a s regards both labour costs and the costs of supervision and administration. Studies showed that hand-saw and ladder pruning was quicker, more eff ic ient, and more preferred by the worker than pole-saw pruning. All the studies showed that l ive-pruned branches heal quickly and cleanly and that branch-stub healing is one of the l esser p roblems in the pruning of young stands of Douglas fir. b v ’- 2