FOREST PLANTING IN THE LAKE STATES 27 
The growth and survival of the trees should be weighed with the 
costs in the choice of a planting method. Slit planting is the least 
expensive. The cost of plowing furrows acids little to the expense 
because it is largely compensated by the reduction in time of actual 
planting. The hole methods are slower and more expensive and are 
only justified on extremely brushy or rocky sites. Costs are dis- 
cussed in more detail in a later section. However, considering them 
in general terms along with growth and survival, the conclusions in 
regard to methods of planting may be summarized as follows : 
Slit planting with a planting bar or spade is the quickest and 
cheapest method of setting the trees and results in satisfactory 
growth and survival. However, all of the methods have usually been 
successful, and the differences between them in survival and growth 
are small. The greater costs of the more expensive methods are not 
justified by any prospect of more than partial compensation in the 
form of more rapid growth, greater survival, higher yields, or 
higher quality of product. 
The trees should be planted in furrows wherever plowing is 
possible. 
SPACING OR NUMBER OF PLANTS TO THE ACRE 
The number of trees that are planted on an acre, or the distance 
between trees, is important because it affects the cost and returns of 
planting and the amount and quality of timber that will be obtained 
from the plantation. Usually the trees are planted in parallel rows 
and spaced equally in the rows, each four trees forming a square. 
Actually, however, it makes no difference whether the trees in a row 
are exactly in line with those in adjacent rows. Similarly, for fur- 
row planting the rows need not and can not be exactly straight or 
parallel. Triangular spacing, requiring more trees to the acre for 
the same spacing is also satisfactory, but it is less easy to organize 
the work and planting crew for this than for the rectangular system. 
Plantings have been made with spacing between the trees varying 
from 3 by 3 feet to 10 by 10 feet. The smallest spacing, which re- 
quires 4,840 trees to an acre, is too close for the best results, and the 
largest, which requires only 435 trees to the acre, is too wide. A 
large proportion of the plantations on the national forests have been 
made with TOO to 800 trees to the acre, which is the equivalent of a 
spacing of about 7 by 8 feet. These numbers are supplemented 
usually by 100 to 200 trees to the acre of natural jack pine and oak 
which are found on most of the planting sites. The Wisconsin and 
Minnesota State Forest Services in their recommendations to private 
owners have usually suggested 6 by 6 foot spacing, or 1,210 trees to 
the acre. On the State forests in Michigan closer spacing has been 
used, varying from 3 by 3 or 4 by 4 feet in some of the earliest plant- 
ings to an average of 1,500 or 1,700 trees to the acre spaced 5 by 6 or 
5 by 5 feet over large areas in the bulk of the State planting. 
For Norway, northern white, and jack pine, and white spruce, 5 by 
5 to 8 by 8 spacing should be used. Six by six feet or 1,210 trees to 
the acre can be recommended. At this rate the branches of the trees 
come together when they are from 10 to 20 years old. The lower 
branches of the pines begin to die from shading between the ages of 
15 and 25 years, when they are not more than 0.75 inch in diameter 
