Yearbook^ of Agriculture 1949 



ary 15, and avoid asphalt tree paints 

 during that period; disinfect all prun- 

 ing tools before use on healthy syca- 

 mores between February 16 and 

 November 30. Denatured alcohol used 

 as a dip or swab is a satisfactory disin- 

 fectant. If wound dressing is necessary, 

 use a gilsonite-varnish paint into which 

 0.2 percent phenylmercury nitrate has 

 been mixed. For districts where the 

 disease is not established, observe these 

 precautions : Disinfect all of the prun- 

 ing equipment thoroughly before the 

 work begins; use new paint brushes 

 and pots. 



Most of the authorities are pessimis- 

 tic about our ability to check entirely 

 the Dutch elm disease or phloem 

 necrosis, and at the moment we can 

 only try to isolate them and to slow 

 down their spread. The canker stain of 

 sycamores, while serious enough, offers 

 greater hope of checking and perhaps 

 even eventual eradication or isolation. 



We have listed the principal epi- 

 demic tree diseases which we are fight- 

 ing today, but we must be alert for 

 others which might appear at any time 

 and alert to diseases which are chronic 

 now but which might become epidemic. 



In planting trees on the home 

 grounds, in the squares and circles, the 

 parkways, and large city parks, the 

 determination of varieties hinges on 

 the effects desired and factors of natu- 

 ral elevation and exposure that the 

 trees require. There are several sign- 

 posts to guide one in making the selec- 

 tions for those sites. 



A good street tree is one that pro- 

 vides shade and ornamentation, keeps 

 within the bounds required of its 

 growth, does not interfere with vehic- 

 ular or pedestrian traffic, and stays 

 healthy. 



Streets of different widths require 

 trees of different shapes and sizes. A 

 narrow, pyramidal, or columnar tree 

 is indicated for the narrow street with 

 a limited building set-back; a narrow 

 street cannot accommodate a broad 

 specimen red oak or sycamore, but 

 Lombardy and bolleana poplars are 

 well adapted to this type of planting 



if their roots do not interfere with 

 sewers. Those poplars are softwooded 

 and have a tendency to break in storms, 

 but they are sometimes useful where 

 others cannot be grown. The pyramidal 

 English oak, the fastigiate form of the 

 ginkgo, as well as the pyramid tulip- 

 tree, which are tolerant of smoke and 

 soot, are admirably suited to this use. 

 Where polluted air is not a factor, the 

 columnar sugar maple, the pyramidal 

 red maple, and perhaps the sweetgum 

 will serve the purpose, although the 

 sweetgum is sometimes objectionable 

 because of its falling fruit in autumn. 



The wider streets can be planted to 

 American ash, Norway maple, tulip- 

 tree, sycamore, or the lindens, all of 

 which resist damage from smoke and 

 fumes. Again, if smoke is not prevalent, 

 such trees as scarlet oak, willow oak, 

 pin oak, sugar maple, thornless honey- 

 locust, blackgum or sourgum, and 

 Scotch elm can be used effectively. 



On the broadest avenues and boule- 

 vards there is opportunity to use large, 

 massive tree types. Unfortunately, most 

 of these broadheaded varieties are sus- 

 ceptible to the gases, smoke, and soot. 

 The patriarch red oak, white oak, 

 black oak, willows, and even the larger 

 pines, spruces, and firs can be effec- 

 tive in the wide parking along such 

 thoroughfares. 



The limitations of space imposed by 

 streets do not apply in our selection 

 of trees for large city parks and park- 

 ways, institutions, or residence grounds. 

 There we have an opportunity to plant 

 the more common, better-known spe- 

 cies as well as add greatly to the interest 

 and variety of the landscape by the use 

 of the rarer and more unusual sorts. 



Many trees of outstanding beauty are 

 too sparingly used simply because one 

 does not know them. Pink and white 

 dogwoods are unsurpassed of their sort, 

 but how many people know and use 

 the Chinese and the Kousa dogwood, 

 whose blooms come after the foliage 

 has appeared? Most of us know the 

 redbud, or Judas-tree, but how many 

 are familiar with the beautiful white 

 form of this spring bloomer? 



