12 BULLETIN 1113, U. S. DEPARTMENT OF AGRICULTURE. 
DECIDUOUS OR HARDWOOD SPECIES INTRODUCED TO THE REGION. 
Carolina poplar. — The Carolina poplar (Populus sp.) is propa- 
gated by commercial nurseries and lias been widely used in past years 
for shelter-belt planting on the prairies east of the northern Great 
Plains region. It is probably a selection of the common cottonwood 
taken in the central or eastern United States. Extensive tests with 
this variety in shelter belts on the northern Great Plains have proved 
it entirely unsuited for general planting in this region. 
Norway poplar. — The Norway poplar (Populu* sp.) is propagated 
extensively by commercial nurseries. It closely resembles the Caro- 
lina poplar. Extensive tests in shelter-belt plantings in the northern 
Great Plains indicate that it is unsuited for general planting in this 
section. 
Canadian poplar. — The Canadian poplar {Populus sp.) is one of 
several varieties imported a number of years ago from northern 
Fig. 6. — Shelter-belt planting of box elder, northwest poplar, and green ash planted 6 by 6 
feet at Archer, Mont., showing clean cultivation in the first year of growth. 
Russia or Siberia and propagated by commercial nurseries in the 
United States and Canada. This variety has been extensively 
planted in the Plains region of Canada, where it has proved quite 
adaptable for shelter-belt use. Plantings in the Plains region of the 
United States, however, have shown that it is subject to attack by 
canker, which kills the trees in three or four years. This disease 
makes it a questionable variety for general use in this region. 
Laurel-leaf willow. — The laurel-leaf willow (Salix pentandra) is 
extensively propagated by commercial nurseries for shelter-belt 
planting in the Northwest. It was imported a number of years ago 
from Europe. While it is reasonably hardy, it does not seem able to 
establish itself in the upland prairie locations on the Great Plains. 
Extensive test plantings have grown nicely for one or two years 
and then killed out for what seems to be lack of sufficient moisture. 
