CHAPTER XI 

 PLANTS FOR USE IN CONGESTED CITY DISTRICTS 



The eflPect of dust, smoke, and gas fumes upon vegetation is well 

 known and yet no considerable amount of study has been given 

 to this subject, largely because it has not been considered an eco- 

 nomic question. Surely the people who are compelled to Hve in the 

 congested districts of our large cities are as much entitled to shade and 

 greenery as any one else, and there is no question but that the health- 

 fulness of the congested districts is lowered by the absence of shade and 

 grass. By the use of those plants which can survive drought, smoke, 

 and abuse, some sort of trees or shrubbery may be had almost any- 

 where, except perhaps in the immediate vicinity of a steel mill or 

 similar factories, where not even grass will survive. The first trees 

 one comes to on the edge of the treeless districts which surround large 

 steel mills are usually ailanthus or willow. The ailanthus is also the 

 tree which most often appears in the closely built up sections of large 

 cities, often providing the only greenery to be seen in whole sections of 

 a town. Ashes, locusts, European planes, European lindens, and horse- 

 chestnuts also seem to have the ability to withstand the summer 

 droughts and the suffocating soot that proves disastrous to so many 

 city trees. No rough-leaved tree nor one which requires much water 

 should be used as a street tree in a congested, sooty district, because 

 it is doomed beforehand to a lingering death, if it survives at all. 

 Pin oaks and willows are useful only when they are assured of a 

 reasonable supply of water during summer droughts. 



Among the shrubs such smooth-leaved, hardy sorts as the lilacs, 

 privets, golden bells, buckthorns, and barberries seem to withstand the 

 drawbacks of smoke, soot, and drought the best. 



Most of the coniferous evergreens have a hard time even existing 

 in any closely built up town. The Colorado blue spruce, silver fir, 

 Scotch pine, and dwarf mountain pine have withstood the soot and gas 

 better than any others, and some recent experiments with the Carolina 

 hemlock seem to show that it, too, will survive in the heart of a city, 



xx8 



