34 



BULLETIN 933, U. S. DEPARTMENT OF AGRICULTURE. 



factory development of plantations. It affects the crown density 

 and directly limits the number of trees to the acre under which the 

 proper growing conditions may be maintained and the best material 

 produced. The number of trees to the acre required to maintain a 

 continuous crown cover is, of course, largest in the early history of 

 a plantation and decreases with age, either naturally, through the 

 crowding out of the less rapid growing individuals, or under manage- 

 ment through their removal in thinnings. In the case of walnut 

 close spacing (see " Spacing," p. 42) at the start is more practicable 

 than with many other species, because of the relatively low cost of 

 nuts and planting. This close spacing tends to reduce, although it 

 can not always prevent, the profuse branching of the trees at a 

 height of about 6 feet. When, however, the crowns commence to 

 crowd each other badly, some beginning to take the lead and others 

 to fall behind, it is poor economy to maintain such a density, and 

 thinnings become imperative. Left to themselves, these even-aged 

 plantations develop so uniformly that the dominant trees do not 

 much exceed their lesser neighbors in height, the thrift of the whole 

 stand is lowered by mutual suppression, and the stand is in a condi- 

 tion of stagnation. Ultimately, the crowns become very much re- 

 duced and stag headed, and water sprouts come out profusely on the 

 trunks. These water sprouts grow slowly until the tree dies or is 

 released by the death of neighboring trees; whereupon the sprouts 

 take a new lease of life, and the tree develops into a topless branchy 

 stub of no use for any purpose. 



The combined effects of poorly chosen site and overcrowding are 

 shown in a plantation in Jackson County, Mo. Although the plan- 

 tation is 82 years old, few of the trees are merchantable. The stand 

 is situated on a hilltop, which, in this western region, is too dry for 

 walnut ; consequently, the trees of the outermost row, exposed to full 

 light on one side, have poor development, branch low, and are prac- 

 ticall} r worthless. The effects of overcrowding upon the condition 

 both of the trees inside the plantation and of those in the outer row 

 may be summarized as in Table 14. 



Table 14. 





Average 



diameter 



breast 



high. 



Percentage of total number of 

 trees. 





Healthy. 



Water 

 spouted. 



Decayed. 





Inches. 

 17.1 



(>5 

 34 



18 

 63 



17 





12.7 



3 







