108 SHADE-TREES IN TOWNS AND CITIES 



to twenty-five gallons at every watering. Older trees re- 

 quire more water. It must always be borne in mind that 

 enough water should be used to penetrate the soil in which 

 the roots of the tree extend. Watering at intervals of every 

 week or ten days will, on the average, be found sufficient if 

 every time the soil around the roots is thoroughly saturated. 

 While on the one hand there must be enough watering to 

 maintain a uniform degree of moisture in the soil, on the 

 other hand care must be taken not to allow too much mois- 

 ture around the roots. 



How to Water. — When watering is provided for by a sys- 

 tem of subirrigation of tile pipes, the process is simple, as 

 the necessary quantity of water can be supplied through the 

 branch pipe carried to the surface. When there is no such 

 provision made for watering, the soil around the base of the 

 tree should be thoroughly loosened and a shallow basin 

 formed around the tree about eight inches deep. The size 

 of this basin will depend upon the extent of the roots of the 

 trees desired to water. Ordinarily the extent of the roots 

 of trees is about the same diameter as that of the crown. 

 The deepest part of the basin should be the portion farthest 

 away from the stem of the tree. When trees have grills, the 

 soil underneath should be left depressed in the form of a 

 basin, to permit of watering. 



The water is applied from a hydrant or from a watering- 

 cart, and is allowed to run slowly, so that all of it will soak 

 into the soil. Before the soil hardens and packs, the loose 

 soil that was removed to form the basin should be replaced, 

 and the ground brought to grade. By keeping the soil por- 

 ous the moisture is retained for a longer period of time. In 

 the city of Paris watering devices, covered with grills, are 

 installed in the intermediary spaces between very large 



