38 BULLETIN 13, U. S. DEPARTMENT OF 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. 1 
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 
i 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 priming to second-growth white 
pine is the stand belonging to and managed by Mr. O. M. Pratt, Holderness, N. H. 
