Shade Trees for the Rockies 



75 



to the plateau as a whole, but even 

 with the best of care and conditions it 

 grows slowly. 



London planetree, a slow-growing 

 but attractive tree, has a crown of deep- 

 green leaves on a grayish- white, smooth 

 stem. It makes a fine street tree where 

 it can be planted in rich soil with ample 

 irrigation. It is not recommended for 

 the mountains or the cold plateaus of 

 northwestern Colorado. 



The closely related sycamore has 

 much the same characteristics and re- 

 quirements but is less desirable because 

 of its susceptibility to a seriously dis- 

 figuring leaf blight. 



Lanceleaf poplar is a clean-looking 

 tree with moderately dense, light-green 

 foliage and smooth, greenish bark. It 

 is recommended for mountain areas 

 only. 



Narrowleaf poplar resembles lance- 

 leaf poplar but is better adapted to 

 lower elevations. With some care it 

 makes a good street tree at altitudes 

 of 5,000 feet or more. It is subject to 

 attack by several borers, which, if not 

 controlled, will ruin its apearance and 

 shorten its life. 



Lombardy poplar has a narrow 

 columnlike crown of thin, almost up- 

 right, branches. It is better adapted 

 to roadside than street planting. It 

 seldom remains attractive more than 

 20 years, and is commonly killed about 

 that age by an uncontrollable disease. 

 It is not recommended for the moun- 

 tain areas. 



Plains poplar is a distinctive native 

 tree with a low, spreading, irregular 

 crown. It may be used anywhere on 

 the plateau but should be planted only 

 where it will have ample room to de- 

 velop and where there is plenty of 

 moisture. Stock from male, or stami- 

 nate, trees is preferred as it does not 

 produce the bothersome "cotton." This 

 tree is rapidly losing popularity in the 

 cities because it takes so much space, 

 and in the agricultural areas it is being 

 cut as a water conservation measure. 



Russian-olive is a small tree with an 

 irregular-shaped crown of silvery-gray 

 foliage. It has a tendency to assume a 



shrubby habit but can be trained into 

 an attractive tree. It is excellent for 

 color contrast in group plantings. This 

 tree is especially adapted to the high 

 plateau. It is highly resistant to drought 

 and tolerant of alkali. 



Tamarisk has an irregular outline, 

 thin, feathery, gray-green foliage, and 

 white to pink flowers. It is well adapted 

 to dry alkaline soils and will thrive with 

 little care. It should not be used at ele- 

 vations above 5,000 feet or in unusually 

 cold locations, as found in some parts 

 of northwestern Colorado. 



EVERGREENS are worth particular 

 attention. 



Arizona cypress and its relative, the 

 smooth Arizona cypress, have conical 

 crowns of grayish-green foliage. They 

 grow rapidly with irrigation and are 

 especially adapted to the Gila River 

 Basin or the lower elevations below 

 5,000 feet of the high plateau. They 

 will not stand severe, protracted cold. 

 Twig-girdling insects sometimes attack 

 them in force. 



Eucalyptus can be grown only at the 

 lower elevations of the Gila River 

 Basin and even there they may be 

 killed or damaged in the relatively se- 

 vere winters that sometimes occur. Of 

 the several species that have been ex- 

 tensively planted in southern Arizona, 

 the horncap eucalyptus is most toler- 

 ant of alkali and hardpan so prevalent 

 in the area. 



Rocky Mountain juniper, another 

 native of the plateau, frequently is 

 found growing with Colorado pinyon 

 pine. It is a small evergreen tree with 

 a conical crown of greenish to greenish- 

 gray cast. The branchlets often droop 

 and have a weeping effect. This tree 

 can be used effectively as a specimen 

 in formal planting, or in seminatural 

 groupings, as for example, with pinyon. 

 In Denver, with irrigation, it develops 

 into an attractive tree of moderate size. 



Aleppo pine is used extensively in the 

 Gila River Basin as an ornamental or 

 specimen tree but will not grow else- 

 where in the region where winters are 

 more severe. 



