12 BULLETIN 153= U. S. DEPARTMENT OF AGRICULTURE. 



SPACING. 



The proper spacing for trees in a plantation depends largely on 

 the habit of the species and the character of the site. In general, 

 the more tolerant the trees and the more unfavorable the site the 

 closer should be the spacing. White pine is so tolerant that it must 

 be planted as closely as 4 by 4 feet, in order to have the lower branches 

 killed by shading at an early age. Close-spaced stands must be 

 thinned sooner than open-spaced ones, and if the owner does not 

 intend to make such a thinning when needed he should use a wider 

 spacing. With practically all species close spacing requires a thin- 

 ning before the stand is 20 years old, and in the case of some, especially 

 intolerant or rapid-growing trees, such as cottonwood, by the time 

 it is 10 years old. The trees removed in the early thinnings required 

 by close spacing would usually be unmerchantable; hence, if the site 

 is favorable, a wider spacing is usually best. Wide spacing, more- 

 over, reduces initial cost and will give larger trees than can be grown 

 in the same time in a closely spaced plantation in which early thin- 

 nings are not made. 



On the less favorable sites, however, close spacing is best. The 

 greater number of trees per acre offsets the higher mortality among 

 the young plants on poor situations and also gives a thicker crown 

 cover, and hence better protection of the soil. The relatively large 

 amount of falling leaves and litter, moreover, mixes with the soil, thus 

 actually improving it. 



Close spacing gives clearer but comparatively slender boled trees; 

 wide spacing results in more or less branchy trees of comparatively 

 large diameter. This is well illustrated in the case of two plantations 

 of white pine near Clermont, Iowa, on very similar sites. In one 

 of them the trees were originally spaced 1 by 6 J feet and in the other 

 16 by 16 feet. When 43 years old the trees planted 1 by 6 \ feet had 

 reached an average diameter of 7| inches and an average height of 

 53 feet; the lower branches were dead to a height of from 20 to 30 

 feet and were falling off. At the same age the trees planted 16 by 

 16 feet had reached an average diameter of 12.3 inches and an average 

 height of 60 feet, and though the lower branches were dead to a 

 height of from 20 to 30 feet they were still persisting. Of two plan- 

 tations of European larch near Sac City, Iowa, on similar sites, one 

 spaced 8 by 8 feet has, after 28 years, reached an average diameter 

 of 7.6 inches and a height of 47 feet, with the lower branches dead 

 to a height of from 20 to 30 feet. The other, spaced 10 by 12 feet, 

 at the same age shows an average tree diameter of 9.2 inches and a 

 height of 43 feet, the trees having been pruned artificially to a height 

 of 20 feet. 



Old plantations have done much to indicate the relative spacings 

 to which different species are adapted. These spacings are given 

 under the discussions of the respective species. 



