294 rORESTRT INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



with deciduous trees generally this dying off is accomplished more easily than with conifers. The 

 spruces and even the white pine require very dense shading to "clear" the shaft. During this 

 period it is only necessary to weed out the undesirable kinds, such as trees infested by insect and 

 fungus, shrubs, sickly, stunted, or bushy trees which aie apt to overtop and prevent the develop- 

 ment of their better neighbors. In short, our attention is now devoted mainly to improving the 

 composition of the crop. 



WEEDING AND CLEANING THE CROP. 



This weeding or cleaning is easily done with shears when the crop is from 3 to 5 years old. 

 Later, mere cutting back of the undesirable trees with a knife or hatchet may be practiced. In 

 well-made artificial plantations this weeding is rarely needed until about the eighth or tenth year. 

 But in natural growths the young crop is sometimes so dense as to inordinately interfere with the 

 development of the individual trees. The stems then remain so slender that there is danger of 

 their being bent or broken by storm or snow when the growth is thinned out later. In such cases 

 timely thinning is indicated to stimulate more rapid development of the rest of the crop. This 

 can be done most cheaply by cutting swaths or lanes 1 yard wide and as far apart through the 

 crop, leaving strips standing. The outer trees of the btrip, at least, will then shoot ahead and 

 become the main crop. These weeding or improvement cuttings, which must be made gradually 

 and be repeated every two or three years, are best perfoimed during the summer months, or in 

 August and September, when it is easy to judge what should be taken out. 



METHODS OP THINNING. 



During the "thicket" stage, then, which may last from 10 to 25 and more years, the crop is 

 gradually brought into proper composition and condition. When the " pole- wood" stage is 

 reached, most of the saplings being now from 3 to G inches in diameter and from 15 to 25 feet in 

 height, the variation in sizes and in appearance becomes more and more marked. Some of the 

 taller trees begin to show a long, clear shaft and a definite crown. The trees can be more or less 

 readily classified into height and size classes. The rate at which the height growth has progressed 

 begins to fall off and diameter growth increases. Now comes the time when attention must be 

 given to increasing this diameter growth by reducing the number of individuals, and thus having 

 all the wood which the soil can produce deposited on fewer individuals. This is done by judicious 

 and often repeated thinning, taking out some of the trees, and thereby giving more light and 

 increasing the foliage of those remaining; and as the crowns expand, so do the trunks increase 

 their diameter in direct proportion. These thinnings must, however, be made cautiously lest at 

 the same time the soil is exposed too much, or the branch growth of those trees which are to 

 become timber wood is too much stimulated. So varying are the conditions to be considered, 

 according to soil, site, species, and development of the crop, that it is well nigh impossible, 

 without a long and detailed discussion, to lay down rules for the proper procedure. In addition 

 the opinions of authorities differ largely both as to manner and degree of thinning, the old school 

 advising moderate and the new school severer thinnings. 



For the farmer, who can give personal attention to detail and whose object is to grow a variety 

 of sizes and kinds of wood, the following general method may perhaps be most useful. 



First determine which trees are to be treated as the main crop or " final-harvest" crop. For 

 this, 300 to 500 trees per acre of the best grown and most useful kinds may be selected, which 

 should be distributed as uniformly as possible over the acre. These, then—or as many as may 

 live till the final harvest— are destined to grow into timber and are to form the special favorites as 

 much as possible. They may at first be marked to insure recognition ; later on they will be readily 

 distinguished by their superior development. The rest, which we will call the " subordinate " 

 crop, is then to serve merely as filler, nurse, and soil cover. 



WHAT TBEES TO REMOVE. 



It is now necessary, by careful observation of the surroundings of each of the "final-harvest" 

 crop trees, or " superiors," as we may call them, to determine what trees of the "subordinate" 

 crop trees, or " inferiors," must be removed. All nurse trees that threaten to overtop the superiors 



