30 BULLETIN" 149 7, IT. S. DEPARTMENT OF AGRICULTURE 
The differences in diameter are compensated by the differences in 
numbers of trees per unit area, however, so that the volumes of the 
stands of these two spacings would be closely similar at this age. 
For example, whereas of the white pine there might be left on an 
acre 400 of the 435 trees originally planted 10 by 10 feet, 800 out of 
1,740 might be left from a 5 by 5 foot spacing. There was no appre- 
ciable difference in height between the two plantations. The 400 
larger trees would have nearly the same volume per acre as the 800 
smaller ones. The wider-spaced plantation would be ready for cut- 
ting for lumber sooner, but the other would provide an immediate 
small yield in thinnings and a later cut of better-quality lumber, so 
that no positive economic advantage can be shown either way. It is 
likely, however, that plantings 6 or 7 feet apart might give better 
results than either the 5 by 5 or 10 by 10 foot spacing. 
This is an example of the close interrelation between number of 
trees planted per acre, diameter growth of the individual trees, vol- 
ume of wood production per acre, and profitableness of planting. 
When older plantations become available for study and experiment, 
it will be possible to say how these factors can be controlled and the 
maximum profits realized by using the best spacing in planting and 
the right time for thinnings. 
CULTIVATION 
Cultivation of the soil either before or after planting is not neces- 
sary in the region under discussion for the establishment of success- 
ful plantations of pine or spruce, although probably necessary for 
hardwoods and for all kinds of trees in the prairie region of extreme 
western Minnesota. However, cultivation of a plantation stimulates 
the early growth of the trees and assures the survival of a larger 
percentage of them, as it does in smy crop. In an experimental 
planting of Norway spruce, Chittenden (17) found that the culti- 
vated trees grew 2.9 feet and the uncultivated 1.8 feet in height dur- 
ing the four years after planting. The advantage to forest trees, 
however, probably lasts only during the early life of the trees, and 
it is questionable whether the increased growth will offset the cost 
of cultivation. 
TOOLS FOR PLANTING 
Different forms of spades, mattocks, grub hoes, and planting irons 
or bars have been tried and developed for planting work. Six differ- 
ent tools or methods were used in experimental plantings of northern 
white and Norway pine at the Cloquet station (Jfl). These in the 
order of cost were heart spade (at $2.10 per 1,000 trees), wedge spade, 
mattock side hole, cylindrical spade, iron wedge, and mattock center 
hole (at $4.64). All of these but mattock side hole gave over 60 per 
cent survival after two years, except in thick brush, where heavy mor- 
tality resulted regardless of the method. 
HEELING IN 
If the trees can not be planted for several days after they are re- 
ceived, they should be heeled in at or near the planting site. This is 
done by digging a trench with one side at an angle of 45° and deep 
