STREET TREES. 55 



this defect, but when it exists in mature trees it is frequently advisable 

 to connect the branches by a strong chain (fig. 18) in order to prevent 

 the limbs from being torn apart. 



FEEDING. 



It is difficult to do anything to stimulate the growth of street 

 trees after they are once started, because usually the only uncovered 

 area over the roots is the smaU opening immediately about the tree ; 

 hence, the importance of supplying the best of soil well enriched at 

 the time of planting. Sometimes a stimulation is desirable, which 

 can be accomplished by dissolving one-half to 1 pound of nitrate of 

 soda in 50 gallons of water and applying from 1 to 25 gallons of the 

 liquid, depending on the size of the tree. Unless the soil is damp at 

 the time of application water will be needed immediately afterward. 

 This material should be applied only when the tree is in full leaf and 

 growing. If applied when the tree is dormant it is likely to be 

 leached from the soil before it is absorbed. If applied late in the 

 season, that is, within three months of freezing weather, it would 

 likely stimulate a late growth that would be liable to be killed the 

 following winter and might make the whole tree more susceptible 

 to injury from cold. 



Water is one of the great needs of city trees, as the ground surface 

 is often almost completely roofed over with water-tight coverings. 

 It is usually a help for the pavement washings to drain into the parking 

 space where the tree is planted. If a curb is placed about the parking 

 space, frequent, regular watering is necessary where the ground is 

 thoroughly covered with water-tight pavements. 



Where growing under suburban conditions, that is, with streets 

 partially pervious to water, liberal parking spaces, and adjoining 

 lawns, street trees will respond to aU extra care given the near-by 

 open spaces, whether parkings, lawns, or gardens. If these are well 

 cared for the trees shoidd have ample sustenance from them without 

 any direct applications. 



In order to prevent the soil about a tree from being packed too 

 hard by trampling it is frequently desirable on business streets to 

 cover the soil about it with an iron grating. 



SPRAYING. 



Street trees, like all other forms of vegetation, are subject to attacks 

 of insects and diseases. Because of the unfavorable conditions under 

 which they grow, spraying for biting and sucking insects and suitable 

 treatment for borers or other burrowing insects require especially 

 careful attention. 



In addition to a number of troubles common to street trees in gen- 

 eral, each species is liable to troubles of its own; hence, the need of 

 competent supervision by a trained man with an efficient outfit 

 rather than leaving: the work to individual initiative. 



