18 BULLETIN 816, U. S. DEPARTMENT OF AGRICULTURE. 
Region 3.—Region 3 comprises the Sacramento and San Joaquin Valleys. 
The deciducus trees for this region are the California walnut; London plane; Cali- 
fornia and common sycamores; Oregon, Norway, and sycamore maples; white, 
European, and green ashes; red, English, valley, and pin oaks; European linden; 
basswood; English and Huntingdon elms; honey locust; and horse-chestnut. China- 
berries and Texas umbrellas are much planted in these valleys, but are not good 
street trees. Olives and palms are suitable only for formal etiects, while eucalypti 
are satisfactory but are liable to make trouble with defective sewers. Acacias grow 
especially well in this region except in the extreme north. 
Region 4.—Region 4 includes the country from the Sacramento and San Joaquin 
Valleys to the crest of the Sierra Nevada Mountains. It varies in elevation and 
correspondingly in temperature and the amount of available moisture. 
Where there is sufficient moisture, the deciduous trees recommended for region 3, 
except the valley oak and possibly the California sycamore, may be used. Where 
there is less moisture the thornless honey locust, black locust, green ash, hackberry, 
poplars, ash-leaved maple, and the American elm if it can be watered the first few 
years may be planted. In the warmer sections the chinaberry and Texas umbrella 
may be used. 
Region 5.—Region 5 comprises the hot semiarid country of southern California and 
southwestern Arizona which is dependent on irigation. 
The best deciduous trees for this region are those suggested for the Ae portions of 
region 4. With ample irrigation the deciduous trees recommended for region 3 might 
erow. 
Among the evergreens the Texas palmetto, Parkinsonia, and the Washingtonia 
and some other palms can be used where other trees do not succeed. The red and 
desert gums may be used also in the drier regions. With ample irrigation the ever- 
greens suggested for region 2 should succeed. 
Region 6.—Region 6 comprises the’ intermountain section and extends from the 
crest of the Cascade and Sierra Nevada Mountains eastward to the eastern base of the 
Rocky Mountains. The region includes great variations in growing conditions, 
often in very short distances. As a whole it is semiarid, and in most places trees 
can hardly be expected to thrive without more or less irrigation, although in some of 
the mountain valleys and on some of the mountain slopes almost ideal conditions for 
tree growth exist. 
In the drier parts of the region only those deciduous trees that are weeds under more 
congenial conditions can be grown. Those that can be planted with the greatest 
hope of success are the thornless honey locust, black locust, green ash, hackberry, 
and where the others do not succeed, the poplars and ash-leaved maple. Ifit can be 
watered for a few years the American elm usually can be grown, and in the southern 
half of the region the Mississippi hackberry will probably succeed. Near the southern 
border, on lower elevations, the chinaberry and Texas umbrella can also be planted. 
In the locations most favored naturally or where irigation is possible, the trees 
suggested for region 9 can be used. 
Evergreens that may be used for the drier portions of the southern part of region 6 
are the Parkinsonia and the Texas palmetto. 
Native trees may be found that will prove of greater value for limited areas than any 
suggested. Cities and towns contemplating street tree planting would do well to 
consult the nearest State agricultural experiment station or the United States Depart- 
ment of Agriculture if it is thought possible that something better has been found 
than the trees.suggested. 
Region 7.—Region 7 is the northern part of the Great Plains area from the foot of the 
Rocky Mountains at about the 5,000-foot contour line east to the ninety-eighth merid- 
ian. Itis rather uniform in general conditions, the character of soil having no wide 
divergence and the elevation increasing gradually from south to north and east to west. 
