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One other solution, which may lessen expenses slightly was offered for San Diego 

 by one who knows the conditions there. It was based on the fact that the climate 

 of San Diego is of such mildneee that it is not greatly dependant upon shade for 

 its comfort. The idea WES this: 'V/ny not substitute a pergola treatment, with 

 vines, to occur at intervale instead of the trees. Not a lerge formal affair, but 

 a small pergola adapted to the lines of en arbor, of real architectural merit and 

 well planted. 1 This is a tentative idea calling for much more thought before 

 acceptance or rejectance. 



The general requirements of trees are that the soil should be of reasonably 

 fine texture so that water does not drain away too readily or stand too long so 

 that baking is the result afterwards. T/here the soil does not answer these 

 requirements it is highly profitable to make some effort to improve it. In those 

 towns where there is an adequate street cleaning department, the sweepings, pro- 

 vided tney do not contain too much rubcish, are often useful in adding humue to 

 the soil. Where all the earth must be supplied the best possible should, of 

 course, be obtained. 



The old saying that the spread of the roots is proportionate with the spread 

 of the tops, often leads ono to vender how street trees can survive. For them 

 the soil should be at least 1hree feet deep and should be in good condition for as 

 lerge a radical distance from the trunk as possible. With these conditions the 

 trees can usually adapt thwnselves to their other limitations. 



One point which is sometimes over-looked, is that soil which was below the 

 original grade and is now surface soil may or may not be fit soil for planting. 

 In very deep soils, it does not make much difference but usually the first three 

 feet of soil are of better quality than the subsoil. A fill on the other hand 

 often gives good soil for planting, depending, of jourse, upon the original 

 source of the dirt. One danger might possibly arise and that is tnat the fill 

 might be of more porous soil than the original grade with the result tnet the water 

 might stagnate along the old grade level. All these points must be cared for. 



On most streets we find provisions for planting made in strips of parking of 



