Yearbook^ of Agriculture 1949 



In the southern Plains the Arizona 

 cypress is of limited value. 



ERNEST WRIGHT worked in the 

 Great Plains region 7 years before he 

 was transferred to the field headquar- 

 ters of the Division of Forest Pathology 

 in Portland, Oreg. In his work on the 

 Great Plains, Dr. Wright studied the 

 survival of trees in relation to climate 

 and disease. 



T. W. BRETZ, a forest pathologist, 

 conducts investigations on methods of 

 controlling the phloem necrosis of elm 

 in Missouri and nearby States. Dr. 

 Brett? experience includes searching for 

 plant diseases in Iowa and Missouri 

 on the Emergency Plant Disease Sur- 

 vey and teaching and research work in 

 Texas, where he became familiar with 

 conditions in the southern part of the 

 Great Plains. 



SHADE TREES FOR THE ROCKIES 



LAKE S. GILL 



Getting trees to grow along with the 

 settlements and cities of the southern 

 Rocky Mountain region has been all 

 the more impressive because trees are 

 naturally absent from most of the area. 



The region Arizona, Colorado, 

 New Mexico, and Utah is largely a 

 high plateau 4,000 to 8,000 feet in ele- 

 vation and broken by mountain ranges 

 that often exceed 10,000 feet. In south- 

 ern Arizona and southwestern New 

 Mexico, roughly the area drained by 

 the Gila River and its tributaries, the 

 plateau is 1,000 to 4,000 feet in alti- 

 tude. The plateau is largely treeless, 

 although a few species occur along 

 stream banks, and usually the foothills 

 support an open woodland forest of 

 low pinyons and junipers. Coniferous 

 forests, broken occasionally by stands 

 of quaking aspen, cover the sides of 

 the mountains. 



Normal precipitation is less than 16 

 inches a year, only about half of which 

 falls during the growing season. In the 

 Gila Basin the average annual rainfall 

 is less than 12 inches, although there is 

 proportionally more rain in the winter 

 than in other parts of the region below 

 8,000 feet elevation. Precipitation is 20 

 to 30 inches in the mountains. Cold 

 winters and hot summers are the rule 

 except in the Gila drainage, where 

 winter temperatures are usually mild. 

 Wide changes in daily temperatures 

 occur throughout the region, especially 



during the winter months. Late frosts 

 are the rule. Searing winds are com- 

 mon. Most of the soil is alkaline ; much 

 of it is low in nitrogen and poor in 

 physical characteristics. Often an im- 

 pervious layer of hardpan lies close to 

 the surface. 



Under such conditions, the early 

 settlers deserve great credit for intro- 

 ducing new trees. Today Salt Lake 

 City, Denver, and Phoenix are out- 

 standing examples of large cities that 

 have been beautified by shade trees 

 despite natural odds against them. 



At first the plains poplar and the 

 common hackberry, both native, were 

 commonly planted. More recently, the 

 plains poplar has lost favor because of 

 its space requirements, its expansive 

 and high water-consuming root system, 

 and its untidy habit of shedding "cot- 

 ton." The common hackberry is still 

 widely used in difficult locations. 



The black locust and boxelder were 

 among the first introductions to survive 

 the vicissitudes of climate and soil 

 with minimum care. Later the Siberian 

 elm joined them. These three cannot 

 be surpassed in their ability to produce 

 quick shade, stand abuse, and endure 

 unusually unfavorable climatic and soil 

 conditions. 



Today the list of shade trees that can 

 be grown successfully in the southern 

 Rocky Mountains is indeed impressive. 

 Most of them require supplemental ir- 



