28 CIRCULAR 912, U. S. DEPARTMENT OF AGRICULTURE 



Certain strains were found which had a high degree of resistance to 

 winter injury. In the test planting at the Mandan station, many 

 of the trees in inside rows were suppressed by trees in the outside 

 rows. Some trees in outside rows were 50 to 60 feet high. This 

 suppression was responsible for some of the losses in stand. The 

 species responded very favorably to irrigation. It is recommended 

 for windbreak and ornamental purposes under irrigation and on 

 dry-land sites where the moisture supply is favorable. 



Corylus heterophylla. — This species was tested at the Mandan station 

 only. It made a dense, bushy type of growth, which killed back 

 severely during; the drought years of 1934 and 1936. It does not bear 

 much fruit. On the favorable side, it does not have the objectionable 

 suckering habit common to some species of Corylus. It has no value 

 for dry-land windbreak planting. 



Elaeaanus angustifolia. — This species has been extensively planted 

 for windbreak and to a lesser extent for ornamental purposes through- 

 out the area. It showed considerable variability in winter hardiness, 

 depending largely upon soil moisture conditions in the fall. Winter 

 injury usually was heaviest following a wet autumn. Retention 

 of leaves late in the fall makes the trees subject to breakage by sleet. 

 Also, as the wood is somewhat brittle, large trunks are sometimes 

 broken by gusty winds or drifted snow. E. angustifolia does not 

 thrive in shade. Suppression by shade caused much of the injury 

 and loss in the test block. The species is recommended for both 

 dry-land and irrigated windbreaks. The species should not be 

 irrigated during late August or in September, as maturing of the wood 

 and setting of terminal buds would tend to be delayed. 



Elaeagnus umbellata. — Testing of this species was confined to the 

 Mandan station. Winter injury was severe each year, particularly 

 after 1940 when fall soil moisture was higher than average. Heavy 

 losses occurred during the severe drought years of 1934 and 1936. 

 The species has no value for planting in the area. 



Elaeagnus sp. (7551). — This species, originally from northern 

 China, survived for 11 years but killed back heavily each winter. It 

 is not suitable for planting in the area. 



Fraxinus americana. — This species was tested at the Mandan station 

 only. It suffered heavy injury and loss during the severe drought 

 years of 1934 and 1936. Several trees were badly infested with the 

 carpenterworm, Prionoxystus robiniae (Peck). The species is not 

 recommended for dry-land planting but is believed to be suitable for 

 planting under irrigation. 



Fraxinus holotricha. — Testing of this species was confined to the 

 Mandan station. The trees suffered heavy killing back each year. 

 The species is not recommended for planting in the area. 



Fraxinus mandshurica. — This species was tested at the Mandan 

 station only. Killing back was severe after 1947. The species has a 

 very erect form of growth and has a narrow crown (fig. 3). This 

 growth form makes it a desirable type for ornamental purposes if 

 supplemental water is available. It has no value as a dry-land wind- 

 break tree. Leaves are dropped early in the fall. 



Fraxinus nigra. — This species was tested at the Mandan station 

 only. The trees were killed back severely during the drought years of 

 1934 and 1936 and to a lesser extent in other years. Many of the 



