THINNING 147 



growing trees with moderate-sized crowns evenly distributed 

 over the whole area. 



One disadvantage of this method is that by leaving the 

 suppressed poles whose increment is at a standstill, there is 

 a small financial loss, as capital is left uninvested, but this is 

 to a great extent compensated for by the fact that the soil is 

 kept exceedingly clean, to the consequent benefit of the main 

 crop. 



It is difficult to say for certain at what periods of their 

 lives trees require thinning. Much will depend upon the 

 quality of the soil, the situation, and the distance apart at 

 which the trees were originally planted. 



But taking a general average with trees planted 4 feet 

 apart, the first thinning should take place in the case of: 



32 



All thinnings in the early part of a rotation should be 

 slight, except under particular circumstances ; for example, an 

 area under Larch which is badly diseased. 



" Thin little and often " is a sound saying. 



After the first thinning, the operation must be repeated 

 every 5 to 10 years, according to the kind of crop and the 

 density required ; though in the latter stages of a rotation 

 when the principal height growth has ceased, the thinnings 

 are often not so frequent say, every 10 to 15 years. 



Provided other considerations admit of it, light-demanding 

 trees require more frequent thinning than shade-bearing 

 trees, and quick-growing trees than slow-growing trees. 



Trees whose side branches die quickly and easily fall off, 

 as, for instance, Larch, can be thinned relatively more 

 heavily, than trees whose side branches are very persistent, 

 as, for instance, the shade-enduring trees ; and also Oak and 

 Scots Pine up to the first 30 years at any rate. For this 



