28 BULLETIN 149 7, U. S. DEPARTMENT OF AGRICULTURE 
and average only about 0.5 inch. By the time the trees are 25 years 
old, the branches will be dead 10 to 15 feet from the ground. At 
25 to 30 years, when the trees are 4 to 5 inches in diameter, some 
thinning will be necessary. 
With 5 by 5 spacing the crowns of the trees completely shade the 
ground two or three years earlier, the lower limbs begin to die 
sooner and when they are slightly smaller in size. Some of the 
trees should be removed about 15 years after planting. The value 
of the products from thinning these smaller trees will be less, but the 
quality and value of the timber finally cut from the area will be 
higher. On the other hand, with wide spacing of 8 by 8 feet or 680 
trees to the acre, the cost of planting will, be easily one-third less 
than if 6 by 6 spacing is used, the limbs will be larger, the lumber 
more knotty and its value lower, and no product or return from 
thinnings will be obtained until the trees are 40 or 50 years old. 
Tarbox (64) has shown for northern white pine in New England 
that as the number of trees per acre up to 20 or 30 years old is in- 
creased the size of the knots is decreased, and hence the quality of 
the lumber is improved. Similarly, from observations of Norway 
pine in New England Reed (53) has concluded that 4 by 4 foot spac- 
ing is the most desirable for the production of high-quality timber. 
The effect of spacing on the cost of planting and the future ability 
of the timber to earn a certain percentage interest on the investment 
may be illustrated by an example. Assuming all other conditions 
the same, the approximate cost of establishing Norway pine planta- 
tions, as explained later under costs, is $4.50 for 680 trees to the acre 
spaced 8 by 8 feet, $7.50 for 1,210 trees spaced 6 by 6, and $10.50 for 
1,740 trees spaced 5 by 5. If these costs, together with other ex- 
penses, are carried at 5 per cent compound interest for the 60 years 
until the trees become merchantable, the timber will have to have 
stumpage values per thousand board feet of about $11.50 for the 
8 by 8 planting, $15.50 for the 6 by 6, and $19 for the 5 by 5. The 
plantations in the Lake States are not yet sufficiently old to give in- 
formation as to the relative advantages of different densities of 
planting, but it does not seem likely that the possible profits from 
thinnings, or the higher quality and value of the timber from a 
plantation spaced 5 by 5 feet or closer, will more than offset the 
additional cost of planting 1,740 or more instead of 1,210 or less 
trees to the acre. Moreover, it is quite likely that the yield in board 
feet at 60 years of the 8 by 8 foot planting might be greater than 
for the closer spacings. 
The probable percentage of trees which will live is another im- 
portant consideration in determining the proper spacing of a planta- 
tion. The average for the older plantations in the region has been 
given as 56 per cent for Norway pine and jack pine, and 57 per cent 
for northern white pine; 85 per cent is the average for the recent 
large plantings in Michigan. It is desirable to have more than 600 
established trees to the acre during the early life of a plantation. To 
secure this number will require the planting of not less than 800 trees 
to the acre where 85 per cent survival may be expected and not less 
than 1,200 if only 50 per cent of them are likely to live. If allow- 
ance is made for possible heavy losses in unfavorable years, through 
drought or other cause, still larger numbers of trees per acre may 
