i885.] 



AND HORTICULTURIST. 



259 



can be grown. And these two, with the Mahonia, j 

 are, in our experience, the only entirely hardy 

 evergreens which will thrive in our city smoke. 

 The special thriftiness of our Rhododendron and 

 Kalmia beds we attribute to the abundant use of 

 rotten wood as a mulch. It is astonishing how • 

 soon a mulching of 3 or 4 inches of rotten wood 

 will be filled with the small white fibrous roots of 

 these shrubs, and give them vigorous growth. In 

 our e.\perience, trees and shrubs are often found 

 to be " not hardy " from being planted in exposed 

 situations when not in a thoroughly vigorous con- 

 dition. Our habit for quite a number of years has 

 been to plant all shrubbery, which has been 

 transported, in a part of the garden which is well 

 cultivated and where attention can be conveniently 

 given them. Here they will prosper, while on the 

 lawn a majority would either summer die or be 

 winter killed. After say two years of vigorous 

 growth in the garden, they can, on a damp day 

 in spring, be moved to the lawn and seemingly 

 not know of the change. Cleveland, Ohio. 



[We should look on Azalea mollis of equal 

 hardiness with any species of Azalea. The re- 

 marks of our correspondent on hardiness in gen- ! 

 eral are very much to the point. Hardiness is 

 dependent on many things besides frost. Two : 

 plants of the same variety, side by side, will often 

 have one taken and the other left during a severe : 

 winter. Very much depends on constitution, and 

 constitution often depends on food. A well-fed 

 plant will get through a hard winter, when a 

 starved one easily succumbs. 



The note on Rhododendron culture is particu- 

 larly valuable. All experience shows rotten wood 

 as particularly suited to this tribe. — Ed. G. M.] 



DESTRUCTION OF TREES BY COAL GAS. 

 BV H. F. HILLENMEYER. 



The death of trees in cities is frequent and 

 the stereotyped diagnosis is "gas." That gas 

 will destroy trees I doubt not. Illuminating gas 

 is of less specific gravity than air, and if es- 

 caping under ground should rise through it. It is 

 not absorbed by water and should not thus be 

 retained in the soil to the material detriment pf the 

 trees. Escaping gas in the presence of the entire 

 root-system of a tree would likely kill it, but the 

 destruction of part of the roots, or the application 

 of destructive agents to a part only of the roots of 

 a tree would not in my observation do further 

 harm than check the growth in proportion to the 

 injury sustained. 



I have seen many trees perish in the city and 

 have often wondered that tree-life was at all possi- 

 ble. With an impervious stone covering, with no 

 possibility to cultivate or aerate the soil, and with 

 the continuous application of waste slops contain- 

 ing all manner of injurious substances, it is, indeed, 

 wonderful that plant-life is at all possible. 



In Lexington I also notice the loss of which 

 your Louisville correspondent complains. But 

 the cause of the injury is not due to gas. The 

 streets have recently been supplied with water 

 mains and the trees on the sidewalks have been 

 severely root-pruned. The weather in Kentucky 

 has recently been extremely hot, and at Louisville 

 very dry. Here we had abundant rain-falls— nearly 

 \\]i inches during June and July — but before the 

 window at which I write stands a vigorous young 

 sugar maple that on the morning of July 21st was 

 the picture of robust life, and in the evening the 

 leaves on the southwest side might have been used 

 for kindling. The soil was moist and covered with 

 luxurious sod, but with the thermometer on a 

 shaded north portico at 99O, the tree yielded to 

 the open heat of the sun, intensified by reflection 

 and radiation from the contiguous building. 



It is this latter condition that destroys trees in 

 cities. The soil rarely dries, but the pent heat, in- 

 tensified by radiation and reflection, removes 

 moisture faster than the roots can supply it. I 

 notice many trees in Lexington assuming a yellow 

 unhealthy hue, but it is due to root-pruning and 

 to heat, intensified by the surroundings. Some 

 will perish, but the lengthening nights and dimin- 

 ishing heat will mitigate the injury. Lexington, Ky. 



[Coal gas, as our correspondent well remarks, 

 is lighter than the atmosphere, and must be pushed 

 up out of the ground when air or water forces its 

 way in ; and yet, if he has dug up trees killed by 

 coal gas, as they certainly are, he will find the 

 newly turned up earth so nauseous with the stench 

 that he would certaintly be convinced that some- 

 thing has been retained, though the mere "gas" 

 has escaped. 



The conditions referred to by our correspondent 

 undoubtedly injure and kill trees sometimes; and 

 yet there can be no more reason to doubt that 

 gas kills trees also, in the mind of anyone who 

 has lived in Philadelphia a few years, than that 

 lightning also sometimes kills them. If it were 

 desirable we could give in detail evidence that 

 would satisfy anyone. This evidence is not merely 

 of the "popular kind" that "knows such and such 

 is the case because it is," but the facts have been 

 carefully gone over by scientific experts. We need 



