FORESTRY AND CONSERVATION 361 



short, 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 in- 

 terfere 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 devel- 

 opment of the rest of the crop. This can be done most cheaply by 

 cutting swaths or lanes one yard wide and as far apart through the 

 crop, leaving strips standing. The outer trees of the strip, at least, 

 will then shoot ahead and become the main crop. These weeding or 

 improvement cuttings, which must be made gradually and be re- 

 peated every two or three years, are best performed during the sum- 

 mer months, or in August and September, when it is easy to judge 

 what should be taken out. 



Methods of 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 6 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 heignt 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 re- 

 ducing 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 re- 

 maining; and as the crowns expand, so dp 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 disrossion, 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 fol- 

 lowing general method may perhaps be most useful : 



determine which trees are to be treated as the main crop 



