12 



EXPERIMENT STATION WORK, LI. 



These guards should be removed as soon as the trees attain the size when 

 binding is likely to take place. Such binding is likely to force the upper part 

 of the trunk to grow out over the top of the guard and so lessen the strength of 

 the tree, if not completely to girdle it. 



In some cities ordinances provide penalties for the hitching of horses to 

 trees on the highway, and such ordinances should be enforced. * * * Each 

 community must expect a certain amount of accidental injury from this source ; 



but no community should permit the custom to 

 prevail of making a hitching post of a tree stand- 

 ing in front of a residence. 



Trees that show injury from the above causes, 

 and especially those that have areas of the trunk 

 devoid of bark, should be given attention without 

 delay, the ragged edges of the bark being cut to a 

 smooth edge and the entire area covered with paint 

 or tar to protect the wood during the process of 

 healing. 



The soil along the streets and highways 

 is frequently of a sterile nature. This is 

 particularly true wh'ere big fills or deep cuts 

 have been made. In some cases the soils are 

 too wet and in others they are too dry for 

 favorable root development. 



The trees on city streets suffer most often be- 

 cause of a naturally poor soil and a lack of suffi- 

 cient water supply. City streets that are ma- 

 cadamized, paved, or concreted present a surface 

 layer that shuts off almost completely the natural 

 means by which water may reach the roots, and 

 directs all of the surface drainage into catch- 

 basins and sewers. Thus, trees on such streets 

 are subjected to the extreme of adverse conditions, 

 and their natural vitality and soil adaptation 

 must be such that they can withstand the abnor- 

 mal strain on their vitality or they are certain to 

 meet with an unnatural and premature death. 

 Only a very small percentage of the trees used 

 for city work are of the species best adapted to 

 withstand the conditions. 



A scarcity of water from the surface, together 

 with an abundant supply from the subsoil, fosters 

 the production of deep-seated roots, which are one 

 of the most valuable assets of a good shade tree. 

 On the other hand, a thoroughly water-clogged soil 

 admits no air circulation and increases the tendency to the development of 

 surface roots, which are killed during periods of drought; it also provides 

 avenues for root diseases, and finally leads to the death of the tree. Poor 

 soils bring about the condition often known as " stag-head," the symptoms of 

 which are a stunted and sickly appearance of the tree, the presence of slender 

 and weak branches, and a sparsely scattered yellow foliage. The remedy for 

 such a condition depends on its stage of development when detected. In its 

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