36 CIRCULAR 912, U. S. DEPARTMENT OF AGRICULTURE 



Populus simonii. — This species was tested at the Aland an station 

 only. Winter injury, varying from light to severe, was present each 

 year. Despite the fact that no loss has occurred in stand, the killing- 

 back which has taken place in years of above-normal rainfall prevents 

 the species from being recommended for planting in the area. 



Populus tremuloides. — This species is native to the entire area. The 

 trees are found in ravines, in depressions on the open prairie, and on 

 sites where there is a good supply of moisture. The data indicate that 

 it is not suitable for dry -land windbreak planting, but that it will give 

 satisfactory results when planted under irrigation. 



Populus spp. — These species include the so-called Canadian, Nor- 

 way, and Northwest poplars, the first two of which were extensively 

 planted in the area during the early years of settlement. The last one 

 was widely planted in the area during the period 1922-34. With 

 exception of the Northwest poplar, all species were highly subject to 

 killing back and loss of stand, even before the severe drought years. 

 Leaf rust was present in most years. Trees weakened by any cause 

 became susceptible to borer infestation and canker infection. The 

 Northwest poplar, native to North Dakota, and usually considered a 

 cross between P. sargentii and P. tacamahaca, appeared to be the most 

 drought-resistant species in years of normal rainfall. All of these 

 species are suitable for windbreak planting under irrigation. 



Prunus americana. — This species is native to the entire area. It 

 grows in thickets on some of the more favorable moisture sites. Plant- 

 ings on dry land suffered heavy injury and loss during the severe 

 drought years of 1934 and 1936. The species suckers profusely under 

 cultivation. These suckers give good cover even though the original 

 trees die out. The species is recommended for windbreaks and for 

 wildlife-cover plantings on the more favorable moisture sites and under 

 irrigation. 



Prunus pensylvanica. — This species is native to the extreme eastern 

 edge of the area. It has been tested only at Mandan. The trees 

 suffered heavy winter injury and loss during the severe drought years 

 of 1934 and 1936. The species is recommended only for planting 

 under irrigation. 



Prunus serotina. — This species was tested at the Mandan station 

 only. Some winter injury occurred each year. The trees usually 

 produce an abundance of fruit, which is readily eaten by birds. The 

 species is recommended for wildlife-cover planting under irrigation or 

 on the more favorable moisture sites. 



Prunus virginiana var. melanocarpa. — This species is native through- 

 out the area. The shrubs suffered no appreciable amount of winter 

 injury but became infected with X-disease in the last few years of the 

 test. This infection resulted in the killing back or death of a number 

 of shrubs (fig. 8). As X-disease spreads from chokecherry to domestic 

 stone fruits, it is recommended that this useful hardy windbreak 

 species not be planted close to stone-fruit orchards. 



Pseudotsuga taxifolia. — This species has been planted in very 

 limited quantities as an ornamental. It also is native to some parts 

 of the Plains area of eastern Montana. Winter injury was severe 

 during the drought years of 1934 and 1936 only. Heavy losses in 

 stand occurred in 1936 and 1937. The species is a highly desirable 

 windbreak or ornamental tree, but plantings should be confined to 



