84 SHADE-TREES IN TOWNS AND CITIES 



tree is removed it sends out horizontal branches. After one 

 or two years of growth the trees are again transplanted, and 

 this time the ends of the lateral roots are shortened. As an 

 additional means of preventing the spread of the roots, a 

 plow is sometimes run between the nursery rows. In this 

 manner the transplanting process is continued every year or 

 two, and the roots, being prevented from spreading, develop 

 a compact fibrous bundle near the stem. As a result, when 

 the tree is finally moved to be set out on the street, it has 

 all the roots necessary to supply the top. 



Developing of the Stem. — In addition to the development 

 of the root system the main stems of nursery-grown shade- 

 trees are kept free from branches to a height of several feet 

 from the ground by removing the lateral buds or small 

 shoots. The upper twigs are shortened from time to time 

 to produce a well-filled top. 



Limitation of Size. — It is apparent that the processes out- 

 lined above cannot be continued indefinitely, and as a tree 

 becomes larger less of the root system can be taken up on 

 final transplanting. There is, therefore, a natural limitation 

 to the size of the tree that may be most advantageously 

 planted. A larger tree takes longer to recover from the loss 

 of roots and makes little growth; while a smaller one con- 

 tinues its growth after transplanting with the least interrup- 

 tion. It is found that for general planting, trees from two 

 inches and a half to three inches in diameter give the best 

 results. 



From an economic standpoint also the planting of large 

 trees is impracticable. Trees of considerable size, seven or 

 ■eight inches in diameter, set out with the care necessary in 

 such cases, are very expensive; because the frequent trans- 

 plantings of the trees in the nursery bring their final cost 



