

TREES AND SHRUBS FOR THE NORTHERN PLAINS 41 



been used extensively in windbreaks and for ornamental planting. 

 Killing back frequently occurred during dry periods. Bark beetles 

 infested weakened trees during the severe drought periods and made 

 the trees more susceptible to killing back or loss of stand. The species 

 gave an excellent response under irrigation. Under dry-land condi- 

 tions the species gives the best response on the lighter soils. More 

 frequent killing back takes place on the heavier soils. 



Ulmus campestris. — Testing of this species was confined to the 

 Mandan station. Most of the trees suffered frequent winter injury. 

 Such injury was severe during the drought years of 1934 and 1936 

 (fig. 11). The species has no value as a dry-land windbreak tree but 

 may have limited worth under irrigation. A shrubby type of growth 

 makes the species less desirable than U. americana. 



Ulmus carpinifolia var. umbraculifera. — This species was tested at 

 the Mandan station only. Several of the introductions lived for only 

 2 or 3 years. The species is not recommended for planting in the 

 area. 



Ulmus julva.- — This species is native to the eastern edge of the area. 

 It has not been planted to any appreciable extent in windbreaks. 

 Winter injury was severe during the drought years of 1934 and 1936. 

 Some injury during those years was caused also by a heavy infestation 

 of bark beetles. Most of the losses occurred during that time. The 

 species is recommended for planting under irrigation and also on 

 lighter soils under dry-land conditions. 



Ulmus japonica. — Testing of this species was confined to the 

 Mandan station. Winter injury was minor, only tip injury being 



Figure 11. — Some trees of Ulmus campestris were killed to the ground by the 

 middle of summer during the severe drought of 1934. Trees that remained 

 free of winter and drought injury that year killed back severely during the 

 drought year of 1936. The species is recommended for planting under irriga- 

 tion onlv. 



