64 SHADE-TREES IN TOWNS AND CITIES 



year before by putting soil and manure in alternate layers, 

 and turning the pile two or three times in the season to mix 

 them thoroughly. In no case should fresh manure or patent 

 fertilizers be used with the soil. 



Amount of Soil. — The amount and extent of soil neces- 

 sary for the normal development of the root system of trees 

 is about proportional to the spread of the top. It will be 

 readily understood that when trees are planted along side- 

 walk strips, from four to six feet wide, that good soil 

 ought to exist along the entire line of the planting to a 

 depth of at least three feet. It is very seldom, however, 

 in actual planting operations that the entire soil along 

 the planting strip is removed. In the city of Washing- 

 ton, holes for trees are dug eight feet long, three or 

 three and a half feet wide, and three feet deep, the con- 

 tents removed and good soil substituted. This is about the 

 size of holes dug for the trees in the city of Paris. This 

 size of hole and quantity of soil give the trees a good start 

 in life, and insure satisfactory growth for at least five or 

 six years. After that the roots will, in most cases, extend 

 into the ordinary surrounding soil, even if it is not of the 

 best description. If at that time the tree shows signs of 

 restricted growth and early casting of leaves, it will be 

 necessary to supply additional good soil beyond the original 

 excavation when the tree was planted. If the original soil 

 is workable it can be improved by cultivation and fertiliza- 

 tion, so as to supply the extending roots. 



Plantations on excavated ground are generally less favor- 

 ably situated than those on filled-in ground. The surround- 

 ing soil in the former case is apt to be poorer, less workable, 

 and less pervious to moisture than filled-in ground. In the 

 planting of street-trees it is always best for immediate 



