144 MASS. EXPERIMENT STATION BULLETIN 170. 



the effect of the avenue as a whole is aimed at they can be planted closer 

 together. What holds true in regard to trees is also true of shrubbery. 

 Some gardeners plant masses of shrubbery together to get the effect of 

 the whole, while others plant for the individual effects. Trees planted 

 20 or 25 feet apart will interfere in a few years, and if allowed to remain 

 at this distance the individual effect of the tree is destroyed, although 

 such close planting on an avenue is often effective. 



In one city which we recall the elms were planted 25 to 30 feet apart 

 many years ago, presumably with the intention of future thinning, but 

 as no one apparently ever had the courage to do this, the trees have now 

 so developed as to interfere, and as a result have become deformed through 



crowding. It is now too late 

 to practice thinning on these 

 streets. While their indi- 

 vidual characteristics are de- 

 stroyed by their restricted 

 development, yet it must be 

 confessed that the high 

 Gothic arch effect produced 

 by such close planting is 

 effective. 



When trees are planted 

 very closely, every other one 

 can eventually be taken out. 

 The principal difficulty with 

 this method is the courage 

 required to do it; besides, 

 in most places a hearing 

 would have to be given for 

 their removal which might 

 meet with strong opposition. 

 In one instance ash trees 



were planted in a row 25 feet apart. The limbs touched in twenty years, 

 and later every other tree was removed, leaving the trees 50 feet apart. 

 At their present rate of growth it will be some years before they interfere 

 with one another. 



The limbs of medium-sized rock maples planted 40 feet apart will inter- 

 fere, as will those of larger trees of this species when planted 60 feet 

 apart. A good average distance for planting most street trees, however, 

 is 45 to 55 feet. Even 70 to 80 feet is not too far apart to plant elms in 

 some localities, as this tree grows to a large size, with a wide spread of 

 foliage, and we are familiar with specimens of rock maples growing along 

 a roadside which have a spread of 75 feet. For smaller trees, such 

 as the European linden, 30 feet apart is not bad. Many maples are set 

 50 feet apart, and in localities where the development is slow and they 

 do not attain a large size, even 40 feet apart is suitable. When the growth 



FIG. 15. Street with tree belt, showing close 

 planting. 



