TREES AND SHRUBS FOR THE NORTHERN PLAINS 33 



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Figure 6.- — Trees of Pinus edulis (foreground) made little progress in height in 

 11 years. Terminal growth killed back each year. The species is not recom- 

 mended for planting in the area. 



mended for planting only on sandy soils that have a high water table 

 or on soils that can be irrigated. 



Pinus contorta var. latifolia. — This species is native to the western 

 part of the area. It has been used to a very limited extent for wind- 

 break planting. Only minor winter injury has ever occurred. The 

 data indicate that the species has promise for windbreak planting in 

 the area. 



Pinus edulis. — Testing of this species was confined to the Mandan 

 station. Terminal growth was killed back each year and the trees made 

 small progress in height (fig. 6). P. edulis is not recommended for 

 planting in the area. 



Pinus flexilis . — Testing of this species was confined to the Mandan 

 station. It is native to the higher elevations in the western part of 

 the area. A small stand of native trees was discovered in south- 

 western North Dakota in 1942 by Richard Williams. Although the 

 trees in the test block made little growth during the first 8 years, 

 good progress was made after that. The trees suffered no winter 

 injury. Data indicate that the species is satisfactory for windbreak 

 planting in the area. 



Pinus nigra. — A small number of plantings of this species has been 

 made in the area. The trees suffered minor killing back in some years 

 and severe killing back in a few — as in 1942, when the temperature 

 suddenly dropped to 16° F. in mid-September. The species should 

 be planted only on the more favorable moisture sites or under irriga- 

 tion. It is best adapted to the southern part of the area. 



Pinus ponder osa. — This species, native to the western two- thirds of 

 the area, has been planted extensively in windbreaks. Winter injury 

 was of a minor nature except in suppressed trees, which frequently 

 suffered severe injury. The species will not thrive in shade. The 



