44 



EVERGREENS OF COLORADO 



growth ceases. In this state timberline lies commonly at about 11,500 

 feet elevation, although this varies to quite an extent with the exposure, 

 in some sheltered places the occurrence of stunted timber being found one 

 thousand feet higher up. 



The characteristic tree of the sub-alpine zone is the Engelmann spruce 

 which forms great forests of splendid specimens in the more favored sit- 

 uations, with balsam fir as a frequent admixture. As timberline is ap- 

 proached, the limber pine and foxtail pine may be expected to appear 

 upon the exposed slopes or clinging to the crests of wind swept ridges as if 

 to defy the elements. 



The growth of trees at timberline often presents a weird sight. Here 

 the struggle of the trees for a bare existence is shown in their stunted, 



Fig. 29. 



Douglas Fir. b. Blue Spruce. Showing- different behavior 

 of their bud scales in spring. 



grotesque forms which frequently hug the very earth as if to escape the 

 wrath of the elements with which they must contend. 



The fifth or alpine zone extends from timberline to the summits of 

 the higher mountain peaks and, like the first or plains zone, is treeless but 

 not for the same reason. Thus upon the plains it is a matter principally 

 of soil moisture and when this is supplied by irrigation, many species of 

 trees can be made to thrive. In the alpine zone, however, it is largely 

 the very short growing season, together with high wind velocity and low 

 temperature of the soil, which prohibits the growth of trees. 



USES OF OUR EVERGREENS. 



Evergreens for Ornamental Planting. Among the evergreen trees of 

 Colorado are to be found some of the most ornamental trees for landscape 

 gardening purposes. On the home grounds, if rightly placed and properly 

 cared for so as to secure a healthy growth, they are capable of adding 

 much to the foliage effects of summer and of lending a pleasing touch of 



