THINNING 33 



In a pure larch plantation the risk of de- 

 struction by the larch disease is a very real one. 

 The health of the trees should be the first object 

 of the owner. A free circulation of the air is 

 the best way of checking disease. If, therefore, 

 at any time serious signs of disease are present, 

 the plantation should be thinned until the air 

 circulates freely. It is possible that a thinning 

 heavy enough to produce this result may so 

 reduce the density that it will not be sufficient 

 to induce upward growth or to prevent the 

 growth of unsightly side boughs. These dis- 

 advantages must be accepted by the owner. 

 Stunted and knotty trees are preferable to trees 

 destroyed by disease, and if the disease should be 

 early checked there is some hope, that the trees 

 may resume vigorous and satisfactory growth. 



As a rule, in pure larch plantations the natural 

 density does not require artificial interference 

 until the trees reach a height of about 15 feet. 

 At this period there should be a thinning to 

 remove all trees that are dead or so completely 

 suppressed that they are certain to have no 

 more useful growth, and trees that are seriously 

 diseased. A slightly diseased tree need not 

 necessarily be removed, for such frequently 

 recover. 

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