region are situated at a high altitude where the climatic conditions
are severe and frosts are common throughout every month of the
year. In such locations only the most hardy trees will succeed.
Other areas are deficient in moisture, and where this deficiency is
so great as to prohibit the growing of agricultural crops by dry
farming it is useless to attempt growing trees without irrigation.

Probably the tree most commonly planted in treeless regions has
been some species of cottonwood. Lombardy poplar and Balm of Gilead
have been great favorites. Cottonwood grows rapidly and is hardy
against frost, but requires a never-failing supply of water within
five to twenty feet of the surface. Because of its demands for
moisture it will not grow on uplands, but thrives along water courses
or where there is plentiful supply of moisture below the surface. Its
fuel value is not high, though the quantity of its wood production
compensates for its poor quality, nor does it make good fence posts.
Where quick growth is the main consideration, however, it is a good
tree to plant. The varieties known as Norway and Carolina poplar
are the best.

Green ash and hackberry are also hardy against both cold and moisture,
but of slow growth. Their wood is durable in contact with the soil,
making them suitable for fence posts. Where it succeeds black locust
combines many of the desirable qualities to the highest degree. It
is a rapid grower, makes excellent fence posts and has high fuel
value. It is not as hardy against frost as cottonwood and ash,
and while it has been planted successfully in sheltered locations
on high plateaus, its success where frosts occur during the summer
months is problematical. A closely related species, honey locust,
is more frost-hardy but less desirable in other respects, though an