﻿38 BULLETIN 13, U. S. DEPARTMENT OP AGRICULTURE. 



In quality II situations, where the growth is slower, thinnings 

 should be made lightly and often, in order not to expose the soil too 

 much. Because of the relatively low returns to be expected from 

 quality III stands, unremunerative thinnings in them may not be 

 advisable. When enough fuel wood can be cut to make thinnings 

 pay, however, one or two may be made with advantage. 



The amount of wood removed in thinnings, irrespective of the age 

 of the stand, is usually from 15 to 40 per cent (average about 26 

 per cent) of the total volume. It is less in previously thinned than in 

 unthinned stands. The number of trees removed varies widely with 

 the age of the stand and its past density. Ordinarily it ranges 

 between 20 and 60 per cent, with an average of about 45 per cent. 



Pruning has usually been condemned as expensive and likely to 

 produce pitch pockets and loose knots, and at present is not widely 

 practiced. While certain defects often result from pruning, these 

 are in most cases due to wrong methods, and should not be considered 

 evidence against pruning in general. There is reason to believe 

 that if properly done the money expended in pruning will yield 

 substantial returns. 



Pruning should remove all dead branches, and usually a whorl or 

 two of the lower live branches, flush with the trunk. Care should be 

 taken not to injure the trunk; the saw is perhaps the safest and best 

 instrument. By mounting it on a light 12-foot pole, the branches 

 can be pruned to a height of 17 feet, thus providing for a clear lumber 

 increment over one 16-foot log. The cost will be from 5 to 10 cents 

 per tree. Pruning can be done at any season, but for live branches 

 late fall or early winter is probably best, since the tree will suffer less 

 from bleeding than at other seasons. 



To be worth while, pruning must be done early in the life of the 

 stand, preferably at an age of from 20 to 30 years, while the branches 

 are still small and there is but a small amount of low-grade lumber 

 at the heart. A safe rule is to prune to a height not over half that 

 of the tree. A clear length of 17 feet would thus indicate a total 

 height for the tree of 34 feet, but it is better to begin pruning when 

 the tree is smaller, increasing the clear length by a subsequent prun- 

 ing. In this way the maximum time is given for the accumulation 

 of clear lumber during the remaining 30 years or more of the financial 

 rotation. 



Only those trees which are to be left until the final cutting should 

 be pruned. For stands which are to be consistently thinned, the 



1 This subject is discussed in detail in "Silviculture of White Pine," by F. B. Knapp (Bulletin 106, Mass. 

 Forestry Association, 4 Joy St., Boston). An example of the application of pruning to second-growth white 

 pine is the stand belonging to and managed by Mr. O. M. Pratt, Holderness, N. H. 



