PROTECTION FROM WINDS. 271 



weakness by obeying the laws of health that intelligence teaches 

 them, often become stronger at middle age than those of robust 

 organization who early waste their vigor by careless disregard of 

 those laws. By studying the nature of trees we may effect similar 

 results with similar care. 



Winter protection from winds must be effected principally by 

 hardy evergreens. Of these the Norway spruce is one of the most 

 rapid in its growth. In itself a beautiful object, it may be massed 

 in pleasing groups, or compact belts, or close cut colossal hedges. 

 The white pine in sandy soils has a still more rapid growth, and 

 is, therefore, suited to form the highest screens. The American 

 and the Siberian arbor-vitaes are naturally so hedge-like in form 

 that the sight of them at once suggests their usefulness ; while the 

 rambling and graceful young hemlock is readily trained into ver- 

 dant screens of exquisite beauty. 



The relative growth of these trees is about in the following 

 order : The white pine planted from the nursery should attain the 

 height of twenty feet in ten years, and forty feet in twenty years. 

 The Norway spruce grows with about the same rapidity, but its 

 growth being relatively less in breadth at the top, its summit gives 

 less check to winds. The hemlock may attain about two-thirds the 

 size of the pine in the same time ; while the arbor-vitses just named 

 may be relied on to make about a foot of growth per year. These 

 facts suggest to intelligent planters the service these trees may be 

 made to render in the capacity of protectors of the weaker species 

 of trees and shrubs. 



The warming power of evergreen trees in winter is not fully 

 appreciated. They are like living beings, breathing all the time, 

 and keep up, and give off their vital heat in the same manner. In 

 a dense forest the cold is never so intense as on an adjoining 

 prairie ; and the difference between the temperature of even a small 

 grove of evergreens, and open ground near by, is often great 

 enough to decide the life or death of sensitive shrubs and trees. 

 In our chapter on the Characteristics of Trees will be found some 

 interesting facts concerning this quality of trees and plants. 



Deep drainage, deep culture, and protection from winds are the 

 three great means to give trees a healthy and rapid development, 



