TREES AND SHRUBS FOR THE NORTHERN PLAINS 27 



m 



Betula sp. (1594). — This species, native to the Killdeer Mountains of 

 North Dakota, suffered periodic injury prior to the drought of 1934 

 and severe injury that year (fig. 2). All trees were dead in the spring 

 of 1935. The species is not recommended for planting in this area. 



Caragana arborescens. — This species has been widely planted for 

 windbreak purposes on the northern Great Plains. It is both cold- 

 and drought-hardy but will not survive in low areas that remain 

 wet for long periods. The species does not thrive as well on very 

 sandy soils as it does on the heavier types of soils. It has proved 

 to be one of the best shrubs for planting in outside rows of windbreaks. 

 Insects frequently defoliate branches and injure terminal growth. 

 This makes the species unsightly. Another unfavorable feature is 

 that leaves drop early in very dry seasons. Despite these objectionable 

 features, the species is highly recommended for windbreak planting 

 except on wet or very sandy sites. 



Caragana frutex. — This species was under test at the station for only 

 6 years, but it had been grown to some extent in the area for a longer 

 period. It proved to be hardy, but lack of height makes it more 

 suitable for ornamental than for windbreak purposes. 



Caragana microphylla var. mandshurica. — This species was tested 

 at Mandan only. It proved to be hardy and appears to be satis- 

 factory for planting in the area. 



Caragana pygmaea. — This species has been used to some extent for 

 ornamental purposes throughout the area. It proved to be quite 

 hardy, but it lacks suitable height for windbreak purposes. 



Caragana sp. (P. I. 107664 3 ). — This species proved to be hardy. 

 It is more resistant to defoliation by insects than are the other species 

 of this genus. Its growth habit is semiprostrate. The species has 

 no value for windbreak planting but would be suitable as an orna- 

 mental or for wildlife cover. 



Caragana sp. (P. I. 108051). — This species, dwarf in growth habit, 

 proved hardy. The slow growth of the species makes it of no value 

 as a windbreak shrub. The sharp spines developed are excellent for 

 wildlife cover but limit its use for ornamental purposes. 



Caragana sp. (P. I. 108332). — This species proved hardy but its 

 dwarf and spiny growth characteristics limit its use to ornamental 

 or wildlife cover purposes. Some of the trees developed a spread 

 of 10 feet. 



Catalpa bignonioides. — This species has been used to some extent 

 in the southern part of the area. The wood of the trees in the test 

 planting failed to mature in the fall and killing back, usually to the 

 ground, resulted. The trees sprouted prolifically from the base each 

 spring and grew 7 or 8 feet during the season. It is not recommended 

 for planting in the area. 



Catalpa speciosa. — Behavior of this species was similar to C. 

 bignonioides. It is not recommended for planting in the area. 



Celtis occidentalis. — This species is native to the eastern half of 

 both North and South Dakota and has been used to a limited extent 

 in windbreaks throughout the northern Great Plains. There was 

 considerable killing back and losses in stand in windbreak plantings. 



3 Plant Introduction number. See p. 3. 



