356 



ARBORICULTURE 



ARBORICULTURE 



prevented by a good layer of loose stones, open at 

 intervals to the air, placed over the surface before fill- 

 ing, or, in some cases, by the use of agricultural tile 

 drains on the old surface at close intervals and so 

 arranged as to facilitate a free circulation of fresh air 

 through the tiles. 



Street trees. 



In the development of towns and cities, the need of 

 trees as a protection against wind has been reduced to 

 a minimum since the closely built houses protect one 

 another. This close building, however, has brought 

 about another untoward condition that needs ameliora- 

 ting; this is the replacing of the vast extent of green, 

 common to the open country, by a motley array of dis- 

 cordant colors. Many of these colors have been demon- 

 strated experimentally and practically to have exciting 

 and debilitating effects on the 

 physical condition of persons. 

 Part of the great utility of parks 

 is to afford urban residents 

 relief from this color excite- 

 ment. As far as possible, the 

 soothing green needs to be 





315. A group of surviving hemlock spruces. 



taken into the city streets to rest the tired nerves 

 through the effect on the eye. Also, the shade helps to 

 reduce the temperature by absorbing the sun's rays; 

 the large amounts of water the tree transpires also helps 

 to cool the air. These beneficial effects make it worth 

 while to expend effort and money to secure well-shaded 

 streets. Figs. 323, 324. 



The conditions in urban communities are adverse to 

 tree growth. Streets are narrow and the trees crowded; 

 roadway and sidewalk are paved with impervious 

 materials preventing both water and air getting into 

 the soil, and effectually keeping in sewer-gas and illumi- 

 nating-gas that may be discharged into it from below. 

 The air is dust-laden from constant traffic, and, what 

 is far worse, contaminated by soot and poisonous com- 

 pounds from numberless badly-fired chimneys. As 

 though this were not enough, there are the self-styled 

 tree-trimmers, knowing nothing of the work, then the 

 linemen cutting ruthlessly, caring nothing for the tree, 

 and with an occasional gnawing horse adding its dem- 



olition. And the sewer-layer, pipe- or conduit-layer 

 and finally the curb-setter do their worst. After all of 

 these, come the insects and diseases that affect trees 

 everywhere and which here find an easy prey because 

 of tho fewer birds in city streets and the weakened 

 condition of the trees. 



The first essential to successful street tree-planting is 

 competent municipal control of all such work. The 

 street trees should be under the care of an unpaid com- 

 mission of three or five men, one named every two years 

 by a local court, or by the mayor, for a term of six or 

 ten years, and confirmed by the legislative body. Such 

 commissioners usually need to be trained, and there- 

 fore they should have considerable experience in their 

 work before coming into full responsibility. The 

 restrictions on the appointment of the executive officer 

 should be stringent, so that only thoroughly trained and 

 experienced men could be employed. The expert should 

 have the full confidence o'f the commission and be the 

 leader in the work. To fill such a position, a man should 

 have thorough knowledge of trees and the soils and con- 

 ditions under which they grow, their characteristics, 

 aesthetic values and habits of growth under city condi- 

 tions, the methods of aiding trees to withstand these 

 conditions, and a knowledge of the insects and dis- 

 eases to which the different species are liable and the 

 methods of combating them. The work is neither for- 

 estry nor pomology, as it has nothing whatever to do 

 with the products of tree growth or the growing of 

 trees for their fruits. 



Powers vi^al to the success of this commission are the 

 right to plant suitable kinds of trees in a proper way, 

 and to collect benefits for work so done; to control 

 absolutely all pruning, removal and care of trees; and 

 the right to invade private grounds for the control of 

 insects and diseases. Of course, sufficient funds must be 

 available to support the work. 



Many city streets are too narrow from building-line 

 to building-line for satisfactory planting. There is 

 absolutely no excuse for this in the newer sections. 

 There should be at least 100 feet from building-line to 

 building-line on any street and on principal streets con- 

 siderably more. Forty feet may be all that is needed 

 for roadway and sidewalks, at present. The abutting 

 dwellers need the air-space provided by the remaining 

 area which is legitimately used as front lawns. This 

 will leave ample space for trees. If the city grows and 

 more space is needed for traffic, it can be secured with 

 no sacrifice to buildings and the dwellers in the interval 

 have had better living conditions. It is this arrange- 

 ment that makes Washington such a beautiful city, 

 and the lack of it on Fifth Avenue that is costing New 

 York City so much money to widen that thoroughfare. 

 In the older parts of cities, species must be chosen that 

 are appropriate to the width of the street. Most kinds 

 should be planted not closer than 40 feet apart and such 

 varieties as oaks, elms and sycamores would be better 

 at 50 feet. Most planters use 35 and 40 feet because of 

 the public demand for quick shade, and at the greater 

 distances the trees look far apart when first planted. 

 Theoretically, the planting double the number of trees 

 needed at maturity or the placing of fillers of a quick- 

 growing inferior type, is desirable; but practically it is 

 dangerous, as there are not many cases in which public 

 opinion will tolerate the thinning at the proper time. In 

 city work an excavation 2 feet deep, with the removal 

 of at least 2 cubic yards of dirt, should be made for 

 each tree. This should be filled with good top-soil mixed 

 with well-decomposed manure. Of most varieties, trees 

 10 to 12 feet high and 1 Vi to 2 inches caliper should 

 be used. These should be nursery-grown. They should 

 have been frequently transplanted and have a well- 

 developed head, 6 to 8 feet from the ground. The roots 

 should be abundant and fibrous. In planting, the roots 

 should be spread out and separated to their full length, 

 the ground worked all in amongst them, and then thor- 





