1 88 UNIVERSITY OF COLORADO STUDIES 



In the eastern and northern United States poplar is used in large 

 amount for the manufacture of paper pulp. The wood-pulp industry 

 may at some time become important in Colorado where pine and spruce 

 can be obtained ; mills will then be able to use aspen as well. At various 

 points on the north slopes of mountains in southern and western Colo- 

 rado there are groves of aspen on land of little use for growing anything 

 else. Since many of these groves are in the national forest reserves, it 

 is to be expected that the aspen will be used for pulp or for other pur- 

 poses. In view of the increasing scarcity of wood it may be that aspen 

 will be sawed up for crates and boxes, especially light cases such as are 

 used for eggs and fruit. 



Poplars and cottonwoods as shade trees. — Nearly all of our native 

 species have been tried as shade trees in the towns and cities of Colorado. 

 However, the common western cottonwood, the balm-of-Gilead and the 

 lanceleaf cottonwood are the most satisfactory. They are well adapted 

 for planting. They are handsome in form; the foliage, especially of 

 the first named, is a brilliant shining green; they grow rapidly and 

 easily endure extremes of moisture and drouth unless these are greatly 

 prolonged. A serious objection to all the poplars is their short life. In 

 thirty or forty years they reach full maturity and begin to die. Hence, 

 when planted for quick results, other more slow-growing and longer- 

 lived trees should be set out at the same time. Sometimes the "cotton" 

 of these trees is so abundant as to cause much annoyance to housewives. 

 However, if only stamen-bearing trees are planted, or else if the cotton- 

 bearers are cut down, there can be no objection raised on this score. 



The "Carolina poplar," much planted in recent years, has the same 

 good qualities and the same shortcomings as our native species. The 

 Lombardy poplar, well known to everybody because of its tall, spire- 

 like form, is frequently planted and so also is the silverleaf poplar. The 

 latter is certainly desirable as an ornamental tree. 



Autumnal colors. — In the Rocky Mountains there are few trees which 

 show handsome autumnal colors. There are no hard maples and gum 

 trees to turn various shades of orange and red. Hence the colors of the 

 poplars become interesting. The foliage of most of these trees turns 

 yellow and brown in autumn. The common western cottonwood is one 



