124 TREES IN" WINTER 



CHAPTEE VIII 



COMMON" INJUEIES TO SHADE TEEES. 



SOURCES OF INJURY. 



Trees in the city and sometimes those in the country are 

 subjected to many forms of injury. Many of the common injuries 

 are the result of either ignorance or indifference and may easily be 

 prevented. A large proportion of them, however, may be attributed 

 to the unfavorable conditions under which the trees are grown. 

 Many injuries, also, are caused by insects and fungi, but these 

 are discussed in the following chapter. 



^Injuries Caitsed hy Gas and SmoJce — It is a common occur- 

 rence in towns and cities to find trees dying or dead from the 

 effects of gas. The injury may be caused from the presence of 

 gas either in the soil about the roots or in the air about the 

 foliage. Gas in the soil comes from leaking pipes and this 

 trouble may be avoided by the careful laying of gas mains. 

 Municipalities should see that gas pipes are properly laid and 

 corporations should be held responsible for injuries caused by 

 leaking gas pipes. On account of the impervious layer of soil or 

 pavement on the surface, a very small leak will often cause much 

 injury. Sometimes the trees will die gradually, one or two 

 branches at a time, and may survive for several years. On the 

 other hand, cases have been recorded where a whole row of trees 

 has been killed in a single season and from a single leak in a 

 gas main. 



Affected trees will take on a sickly appearance. . The foliage 

 turns yellow and finally falls. The presence of gas in the soil 

 may usually be detected by boring in several places to a depth of 

 three or four feet. A soil auger is a useful tool for this purpose, 

 but where this is not available, a crowbar may be used. The odor 

 of gas in these holes indicates with certainty its presence in the 

 soil. Where gas is found it is well to dig a trench around the 

 trees and to loosen up the soil as much as possible to get rid of 

 the gas. The leak, of course, should be promptly located and 

 repaired. 



Many trees are injured by the coal gas in the air that comes 

 from smoke stacks. Trees in the neighborhood of railway yards 



