TREES AND SHRUBS FOR THE NORTHERN PLAINS 37 



I i 

 : ( 



: 



Vr <— . ~VE 



Figure 8. — Shrubs of Primus virginiana var. melanocarpa badly infected with 

 X-disease. This hardy windbreak species should not be planted near stone- 

 fruit trees, as it is the host for the X-disease. 



irrigated sites or those with very favorable moisture conditions. 



Quercus macrocarpa. — This species is native to most of the area. 

 The trees are both cold- and drought-hardy but have a reputation 

 of being slow growers. Trees grown under clean cultivation on dry 

 land and free of other competition averaged about 1 foot of growth 

 per year. Seedlings are usually difficult to transplant because of 

 their taproot habit of growth. The wood is highly valued for fence 

 posts. The species is recommended for windbreak and wood-lot 

 plantings, both on dry land and under irrigation. 



Rhamnus cathartica. 5 — This species (fig. 9) has been planted to 

 some extent for hedge purposes. It is extremely cold- and drought- 

 hardy and has a shrubby, dense habit of growth. R. cathartica 

 is a highly desirable shrub for windbreak purposes. 



Rhamnus davurica. 5 — This species was extensively planted in the 

 area after the mid-1 930's. It has proved to be both cold- and drought- 

 hardy. The shrubs make a dense growth and can develop a crown 

 spread that equals or exceeds their height. As the wood is very 

 brittle, stems and branches are easily broken by drifted snow. The 

 shrubs are prolific seed bearers. The seed ripens in late October 

 and remains on the shrubs throughout the winter unless eaten by 

 birds. The species is highly recommended for windbreak, ornamental, 

 and wildlife-cover purposes. 



Rhamnus saxatilis. 5 — This species was tested at the Mandan station 

 only. The plantings suffered no winter injury, and the data indicate 

 that the shrub may be very suitable for windbreak planting. 



5 Species of Rhamnus, with the possible exception of R. frangula, which was 

 not tested, are alternate hosts of crown rust of oats. They should not be planted 

 in areas where oats are grown to much extent. 



