THE CARE OF STREET -TREES 109 



trees, the root systems of which have become very exten- 

 sive. Watering of trees should be avoided during the hot- 

 test part of the day. It is best to do it in the early morning 

 and late in the afternoon or evening. In the city of East 

 Orange the watering of the street-trees is done at night, 

 from 7 P.M. to 6 a.m. 



CULTIVATING AND FERTILIZING 



The principal elements in the soil essential to plant 

 growth are nitrogen, phosphoric acid, and potash. It is 

 generally found in cities that it is not the deficiency of the 

 nutritive elements in the soil that causes the decline of 

 trees, but rather the physical condition of the soil which 

 renders it impossible for trees to perform their normal func- 

 tions. The keeping of the soil around trees cultivated and 

 free from weeds is one of the most important aids to their 

 growth. The keeping of the ground loose allows air to 

 reach the roots, renders more available the plant food the 

 soil contains, and prevents the rapid evaporation of mois- 

 ture. If the ground is hard it becomes heated, the water 

 forces itself to the surface, and passes into the atmosphere. 

 If kept cultivated it acts like a blanket, and prevents the 

 loss of water by surface evaporation. 



Too much stress cannot be laid upon the importance of 

 cultivation, the full value of which is not generally appre- 

 ciated. When there is no water available, trees can fre- 

 quently be brought through in good condition during a 

 period of drought by just keeping the soil dug up and loose 

 around their base. 



One of the best ways of improving the condition of the 

 soil of trees is to put a mulching of manure around them in 

 the fall, allow that to remain all winter, and then turn the 



