TREES AND SHRUBS FOR THE NORTHERN PLAINS 35 



conditions but is highly successful under irrigation. Root suckers, 

 which frequently come up at long distances from the trees, are objec- 

 tionable if the trees are near gardens or lawns. 



Populus angustifolia. — This species, native to the western part of 

 the area, suffered heavy winter injury and loss during the severe 

 drought years. It is recommended for planting under irrigation only. 



Populus balsamifera. — This species has been planted to a limited 

 extent in the area. It suffered frequent killing back and heavy losses 

 before the severe drought years. It is not recommended for dry-land 

 sites but would be satisfactory where there is a plentiful supply of 

 water for irrigation. 



Populus berolinensis . — This species was tested at the Mandan 

 station only. Winter injury, while not severe, was variable from year 

 to year. Most of the trees died prior to the first severe drought year 

 (1934). The last ones died that year. 



Populus canadensis var. eugenei. — This species was extensively 

 planted in the area during the early years of settlement. It was not 

 satisfactory on dry-land sites but gave good response under irrigation. 

 The species is susceptible to canker and leaf -rust infection. 



Populus candicans. — This species, tested only at the Mandan 

 station, suffered such heavy winter injury, canker infection, and loss 

 during its early years that it is not recommended for planting in the 

 area. 



Populus deltoides. — Testing of this species was confined to an intro- 

 duction that suffered heavy winter injury and loss during its early 

 years. Many of the trees were badly infected with canker. It cannot 

 be recommended for planting in the area. 



Populus generosa. — Testing of this species was confined to the Man- 

 dan station. The trees made quite satisfactory progress and appear 

 to have promise for planting in the area. 



Populus nigra. — The two introductions of this species tested showed 

 considerable variation. Introduction P. I. 34795 remained free of 

 appreciable winter injury. It is recommended for either dry-land or 

 irrigated windbreak planting. The other introduction, P. I. 34796, 

 suffered heavy killing back and losses before the severe drought years 

 and cannot be recommended for planting in the area. 



Populus nigra var. betulifolia. — This species was tested at the 

 Mandan station only. Winter injury was present each year. Further 

 testing is needed before recommendations can be made for this species. 



Populus nigra var. italica. — This species has been planted to a limited 

 extent in the area. Winter injury occurred most years and losses began 

 early in life. The species is recommended only for planting where 

 there is a plentiful supply of irrigation water. 



Populus petrowskiana. — Testing of this species was confined to the 

 Mandan station. Severe killing back and heavy losses did not occur 

 until the severe drought year of 1934, when a high percentage of the 

 trees died. The remaining trees died in 1935. All trees were badly 

 infected with canker at the time of their death. The species is not 

 recommended for planting in the area. 



Populus sargentii. — This species is native along streams and other 

 moist places throughout much of the area. The trees killed back 

 periodically and heavy losses occurred early in life. The species is 

 recommended for planting under irrigation only. 



