SHELTER-BELT DEMONSTRATION * GREAT PLAINS. 27 
Of the tree species extensively tested, the following seem adapted 
to the climatic conditions generally prevailing: Box elder, green 
ash, white elm. and caragana. 
The following species which have so far been tested only in a 
limited way give promise of being suitable for general planting: 
Northwest poplar, chokecherry. buffalo berry. Russian olive, Black 
Hills spruce, white spruce, blue spruce, Scotch pine, and jack pine. 
Extensive tests of the following species show that they are not 
adapted for general planting: Norway poplar. Carolina poplar. Rus- 
sian golden willow, and laurel-leaf willow. 
Careful preparation of the soil before planting, to conserve mois- 
ture and work out grass and weeds, is a prime requisite for successful 
tree planting. Clean summer fallow is the best tillage method to 
practice for this purpose. 
Clean cultivation after planting is essential to the continued growth 
of young trees. Xeglect in this respect for a single season is likely 
to result in serious damage to the trees. 
Insect and animal pests ma}' cause considerable damage unless 
precautions are taken against them. 
With such trees as box elder, green ash, and white elm, stock raised 
from seed procured from native trees has shown greater hardiness 
than that coming from more southern and eastern localities. Seed 
for propagating any species for planting in shelter belts on the north- 
ern Great Plains should come from a northern source. 
A standard spacing distance for trees in shelter belts has not yet 
been determined. Present data indicate that for the average plant- 
ing site in the area the 4 by 8 feet distance used in these demonstra- 
tions is too close. Further information is needed on this point. 
The experience of these five years of tree planting has shown con- 
clusively that it is possible to start successfully a planting of trees 
on the average upland farm site in the northern Great Plains. 
Future investigation must show whether or not it is possible for 
such plantings to maintain themselves after they have attained their 
maximum growth. 
