ARBORICULTURE 



ARBORICULTURE 



353 



usually knows fairly well the greenhouse plants and 

 herbaceous perennials, which cost most in time and 

 money, but the trees and shrubs he often disregards. 

 This is apparently due to the fact that after being once 

 planted, and often not by himself, the trees and shrubs 

 do not need his perpetual care, and usually grow with- 

 out his aid and interference. 



To the landscape gardener a thorough knowledge of 

 trees is absolutely essential. He ought to know the 

 ornamental properties of the trees, their rate and mode 

 of growth, their peculiarities in regard to soil, situation 

 and climate. As the trees are, after the surface of the 

 ground, the most permanent element of the landscape, 

 they ought to be planted with careful deliberation as to 

 the" intended artistic effect and their fitness to the soil 

 and climatic conditions, for mistakes in planting of 

 trees are afterwards not easily corrected and rarely 

 without injury to the original artistic design. 

 The available number of trees from which 

 selection may be made is large. There are 

 in American and European nurseries and gar- 

 dens more than 600 species in cultivation 

 that are hardy in the northern and middle 

 states. About 250 of them are American, more 

 than 200 from eastern Asia, about 100 from 

 Europe and 70 from western and central 

 Asia. About forty natural families are repre- 

 sented, of which the most important are the 

 Pinacese, Fagaceso, Salicaceae, Rosacese, Legu- 

 minosa, Juglandacea, Sapindace.se, Urticacese, 

 Magnoliacea:, and Oleaceae. The number of 

 all the cultivated varieties and garden forms 

 is, of course, considerably larger than that of 

 the botanical species and may be estimated 

 at about 3,000. Comparatively few horti- 

 cultural varieties are found in American nur- 

 seric.s as compared with European, but this 

 need not be regretted, as horticultural varie- 

 ties are mostly merely curious or monstrous 

 forms. In planting, one must rely chiefly 

 on the types and use the horticultural varie- 312- 



ties sparingly, for restfulness should be the 

 prevailing character of the masses and groups of 



ALFRED REHDER. 



CONTENTS TO THE ARTICLES IN "ARBORICULTURE." 



The cultivation of trees, Mulford, page 353. 



The conifers in particular, Fernow, page 358. 



The transplanting of large trees. Hicks, page 362. 



Types of insect injury to trees, Brues, page 364. 



Some types of tree diseases, Rankin, page 368. 



Choice of trees for special purposes, Rehder, page 372. 



Choice of street trees for special regions, Mulford, page 374. 



Ornamental trees for the middle and southern states, Berckmans, 



page 374. 



Trees on the great plains, Bessey and Watrous, page 376. 

 Trees grown for shade and ornament in California, Davy and 



Morrison, page 378. 



The cultivation of trees. 



From earliest times man's instinct has been to seek 

 the protection of trees. In locating his home the first 

 necessity has been the proximity of water; second, 

 pasture for his flocks; third, the presence of trees; in 

 warm countries it has been necessary to provide pro- 

 tection from the hot sun's rays, in cool countries for 

 the sake of fuel and protection from the elements. As 

 civilization has progressed and man has developed more 

 elaborate abodes, he still desires the protection of trees 

 to make his home more comfortable, to protect it 

 from the winter wind, or the summer sun, or both. 



To meet the needs in different localities, as one or 

 another protection may be more important, different 

 kinds of trees are used. In the extreme North, the conif- 

 erous evergreens act as windbreaks twelve months in 

 the year. In the south Atlantic and Gulf regions, the 

 broad-leaved evergreens give shade the year through. 



23 



In the intermediate country and overlapping both, the 

 deciduous trees afford much summer protection and a 

 little whiter protection. The chief aesthetic value of 

 trees is due to the suggestion of comfort that they 

 give. In whiter, a house snuggling against a group of 

 evergreens may be attractive, and yet, if lacking a well- 

 placed shade tree, may in summer appear glaring or 

 otherwise uninviting. These feelings are the same with 

 regard to native woodlands or man-made clumps more 

 remote from dwellings. The different kinds of forest 

 attract because of suggestions of comparative comfort 

 and of pleasures. To those who have lived in the heart 

 of a large city all their lives, such scenes are likely to be 

 unattractive because of lack of suggestiveness. Some 

 of the interesting and varied forms of trees are dis- 

 played in Figs. 312 to 359. 



In planting trees for ornament, these elements of pro- 



A group of old sugar maples, with irregular and broken heads. 



tection suggest two uses, that of windbreaks and that 

 of producing shade at appropriate places. In addition 

 are the partial hiding of buildings from important view- 

 points, enhancing the beauties of the building or per- 

 mitting only the most desirable features to be seen, 

 covering the outlines of ugly buildings, or completely 

 hiding objectionable objects, either nearby or distant; 

 forming frames for distant views or nearby objects; 

 making knolls and hills look higher by groves on their 

 tops, or valleys look deeper because of wooded sides; 

 making irregular sky lines either by accentuating 

 existing conditions by planting tall trees on the high 

 places and low trees in the low places, or in level coun- 

 tries making a similar sky line by tall and short trees; 

 or forming irregular and natural appearing boundaries 

 to lawns or meadows. 



To accomplish any of these results, some trees are 

 inherently better suited than others; climate and soil, 

 however, may make their use impracticable or impos- 

 sible. Coniferous evergreens make the ideal windbreak 

 and screen, but they are satisfactory only in the north- 

 eastern section of the country and on the Pacific Coast, 

 the hot sun of the South, the dry winds of the central 

 plains and the smoke of cities making most species 

 impossible in those regions. The broad-leaved ever- 

 greens are next in importance, but they are adapted 

 only to the south Atlantic and Gulf seaboards, and the 

 Pacific Coast north of San Francisco. For adaptabili- 

 ties see special lists, for no other sweeping generaliza- 

 tions of adaptabilities can be made except that the use 

 of bronze, yellow or variegated-leaved trees, and trees 

 of unusual drooping habit or of other striking form, 

 should be limited to special times and places. A tree to 

 be satisfactory for ornamental planting must suit the 



