ARRANGEMENT OF TREES ON STREETS. 35 



Trees can be planted, when in double rows, either opposite each other 

 or alternate in the rows. Alternate planting is better adapted for double 

 rows on narrow planting strips since it permits the crowns to interlock in 

 place of interfering. 



ARRANGEMENTS OF PLANTINGS. 



The usual practice of planting at one time the entire length of a 

 street with the same species, all specimens of which are expected to reach 

 maturity together, has some disadvantages. For a long period it is true 

 the effect of the continuous uniform rows is faultless. The trees reach 

 maturity about the same time, but they begin to decline irregularly, and 

 each specimen is cut as it becomes necessary and a replant made. In this 

 manner replanting extends over many years, and even though the same 

 species be used for filling blanks, the original regularity will seldom 

 again be attained. 



When some formality is desired, it is best to make an original planting 

 of two species, one selected for a permanent tree and the other a short- 

 lived, quickly growing tree planted alternately with the permanent spe- 

 cies. The temporary tree will soon furnish shade and give some character 

 to the street. When it reaches maturity or at the end of a fixed period, 

 all specimens of this temporary species can be removed, and specimens of 

 the permanent tree planted in their place. This will give two sets of trees 

 of the same kind, differing in age by a fixed period. The younger series 

 will be in its maturity when the older series is declining. The older series 

 can then be entirely cut and replaced without affecting the continuity of 

 the tree line or seriously impairing the shade. 



• By initiating and strictly adhering to such a plan, the species could at 

 any two cutting periods be entirely changed, if found advisable, and that 

 without interfering with the appearance of the trees or with the shade. 



The distance from the trees to the property line should be the same 

 throughout the length of the street, unless the width of the walk changes. 

 The spacing should be the same between all trees of the same kind so far 

 as they extend on a street and should be determined : ( 1 ) By the species 

 and the size and shape of its crown; (2) by the fertility of the soil, since 

 the crown will attain smaller dimensions on poor than on fertile soils; 

 (3) whether it is intended to permit the trees to attain their full size, as 

 would usually be the case on parking strips, on wide walks, on residential 

 streets where the houses are some distance from the property line, along 

 wide avenues, river drives, etc. See figs. 16, 17 and IS. 



For aesthetic considerations, plantings along a street should be of one 

 species, which should give character and tone to it. While it is unneces- 



