EFFECTS OF PRUNING 157 



time, but it should never take place during a frost. If 

 pruning is done in the summer, the wounds generally heal 

 quicker than if done at any other time ; but the cut surface is 

 more liable to decompose and form a suitable growing 

 medium for fungous spores. 



Where large branches are removed, there can be no doubt 

 that autumn is the best time, for any tar or antiseptic put on 

 the cut surface would fail to penetrate or remain on if the 

 operation took place in the summer or spring. 



Many more experiments are, however, required before 

 this difficult question can be definitely decided. 



(4) The Effects of Pruning. 



The pruning of branches off young trees causes the 

 energy of growth to be directed to the leading shoot ; hence 

 the beneficial effects seen in the case of trees in a young 

 plantation which have hitherto made very little headway, 

 but which, on being pruned, so often begin to " get away " 

 almost immediately. 



Trees approaching maturity which have been well pruned, 

 either naturally or artificially will have a higher form factor 

 that is, they will be more cylindrical and less tapering. 



The reason is because increment in girth is greatest near 

 the top of the bole, usually just below the lowest branch of 

 the crown, provided always that the trees are properly 

 grown. 



A tree with many side branches on the stem, will often 

 have broader annual rings near the base than higher up, and 

 will therefore be very tapering. 



Again, the pruning of side branches will stimulate height 

 growth even in the case of middle-aged trees, provided the 

 period of natural height growth has not ceased and the trees 

 be still vigorous. 



The effect of pruning of big branches on old trees is at 

 times apparently rather contradictory, though not really so. 

 If senile decay be already approaching and the tree be 

 beginning to become "stag-headed," the removal of side 

 branches will determine the soil nutrients to the crown, 



