ATLAS OF AMERICAN AGRICULTURE. 
Figure 51.—A dense, even stand of desert'saltbush with plants about 4 feet high. (Creosote bush.) The 
uniform gray stretches of this plant resemble somewhat the sagebrush areas, and the plant is often called desert 
sage. Where the soil is poor or the moisture^supply deficient the plants are widely spaced. The type is 
limited largelytothe bottom of valleys, but does not grow on soil which is subifrigated. A dense stand is 
characteristic of good agricultural land, of a soil of fine texture and containing a relatively slight amount 
of soluble, salt. Ipdio, Calif. 
Figure 52.—Creosote bush with a sparse growth of annuals. (Creosote bush.) The widely spaced 
plants are about 5 feet high. The thin, dark-green, lacquered foliage contrasts sharply with the light-gray 
color of the desert plantain, which forms an even cover following the winter rains. During the flowering 
period the bushes are covered with yellow flowers, which are soon replaced by conspicuous hairy fruits. 
Creosote bush usually draws its moisture supply from the deeper soil layers, and is therefore not dependent 
on an even distribution of rainfall. It is confined to soil relatively free from alkali. Near Indian Wells, Calif. 
a highly specialized type of agriculture is developed. 
Production ranges widely from alfalfa and small- 
grain crops, produced as hay, to truck crops, citrus 
fruits, cotton, and dates. Cotton production in the 
West is confined largely to this desert, since both the 
long season and the warm climate are favorable. In 
the lower parts of the valleys, especially in Arizona 
and California, are grown the only dates produced in 
the United States, largely on land of the desert salt¬ 
bush type. 
Although most interesting from a botanical point of 
view, the southern desert shrub has not been studied in 
a sufficiently comprehensive way to enable one to pre¬ 
sent clearly the different types composing it. Over 
much of the area these types are recognized with dif¬ 
ficulty, since there is often a great mixture of species. 
Viewed as a whole, the area is most often characterized 
by pure stands. Although it presents great diversity, 
it may be reduced to the following five main associa¬ 
tions, with each of which a number of minor associa¬ 
tions or associes may be correlated: 
Desert saltbush ( Atriplex polycarpa). 
Narrow leaf saltbush (Atriplex linearis). 
Desert saltbush-mesquite ( Atriplex polycarpcu-Prosopis juli- 
flora). 
Chamiso (Atriplex canescens). 
Creosote bush (Govillea tridentata). 
Creosote bush-bur sage ( Govillea tridentata-Franseria du¬ 
mosa). 
Black brush ( Flourensia eernua). 
Yucca-cactus. 
Yueca-cholla ( Yucca mohavensis-Opuntia bigelovii ). 
Joshua tree-wild buckwheat (Clistoyucca brevifglia-Eriog- 
onum fascieulatum). 
Cactus-palo verde (Garnegiea gigantea-C&i'cidium torrey- 
anum). 
Bechuguilla-sotol (Agave lechuguilla-Dasylirion texanum). 
California sagebrush. 
California sagebrush-encelia (Artemisia califomica-Encelia 
farinosa ). 
Wild buckwheat (Eriogonum fascieulatum). 
Mesquite (Prosopis juliflora). 
Cat’s claw (Acacia gregii). 
Mesquite-chamiso (Prosopis juliflora-Atriplex canescens). 
Mesquite-rayless goldenrod (Prosopis juliflora-Isocoma 
coronopifolia). 
Desert saltbush (fig. 51). — The desert saltbush type 
covers extensive areas in California, Nevada, and Ari¬ 
zona, where often it is referred to as desert sage. The 
uniform gray stretches of this plant {Atriplex poly¬ 
carpa) somewhat resemble the sagebrush areas of the 
northern desert shrub. For the most part the plants 
occur in dense thickets from 3 to 4 feet high on fine 
loam soils well supplied with moisture, which is largely 
derived from drainage. On the poorer land, and 
on land from which there is a run-off or which 
receives only the normal rainfall, the moisture supply 
is insufficient to produce a dense stand, and scattered 
plants 2 or 3 feet high and widely spaced are charac¬ 
teristic. This type is limited largely to the valleys, 
where it occurs just above the salt desert shrub, on fine 
loam soils impregnated with a moderate amount of salt 
or alkali. The desert saltbdsh does not occupy land 
which is subirrigated. The agricultural value of land 
characterized by desert saltbush is probably greater 
than that occupied by any other type in the southern 
desert region, and much of the land now under irriga¬ 
tion was formerly thus characterized. A good growth 
of desert saltbush indicates a good deep soil of fine tex¬ 
ture with a considerable amount of alkali. Under a 
system of careful irrigation this land is very produc¬ 
tive. 
Narrow-leaf saltbush. —Where conditions are rela¬ 
tively less favorable for plant growth, due to more c6m- 
pact subsoil with high salt content, the narrow-leaf 
saltbush ( Atriplex linearis) is found. It occurs in 
southern Arizona below the desert saltbush and above 
the seqpweed of the salt desert shrub. 
Desert saltbush-mesquite (fig. 53).—If ground water 
or subsoil conditions are favorable for the growth of 
mesquite, scattered trees occur in the even cover of des¬ 
ert saltbush. This type is usually confined to the lower 
part of the desert-saltbush land in Arizona, Nevada, 
and California, and indicates conditions favorable for 
crop production under irrigation. Here the mesquite 
trees are often large, ranging from 15 to 30 feet in 
height. Sand ridges in the desert-saltbush area are 
often covered with chamiso ( Atriplex canescens). 
Figure 53.—An open stand of desert saltbush with scattered 
mesquite trees. (Creosote bush.) The wide spacing of the desert 
saltbush indicates a relatively deficient soil moisture supply, but 
the presence of the mesquite trees indicates water available in the 
subsoil due probably to a water table within reach of the roots. Las 
Vegas, Nev. 
Creosote bush (fig. 52).—This type of vegetation is 
more extensive in the southern desert than any other 
type, and occupies the region lying between the desert 
saltbush and the yucca-cactus zone above. It is abund¬ 
ant in southeastern California, southern Nevada, west¬ 
ern and southern Arizona, southern New Mexico, and 
extreme western Texas. The plants ( Covillea tri¬ 
dentata) vary from a foot or two to 10 or 15 feet in 
height', depending on the unfavorable or favorable 
moisture supply, and are usually very widely spaced, 
the intervals varying from a few feet to 100 feet or 
more. In Arizona and California, following the win¬ 
ter rains, the spaces between the plants are covered 
with a rather dense growth of annuals, of which desert 
plantain ( Plantago erecta) is one of the most frequent 
(fig. 54). The appearance of the whole is that of a 
widely spaced orchard of small toees or bushes. The 
plants consist of branches which radiate from near the 
ground and form a very open shrub. The shrub ap¬ 
pears very dark green, almost black, as compared with 
the light desert soil and the silvery Plantago. In the 
western part of its range it usually indicates several feet 
of very permeable light soil, well drained, with low run¬ 
off, and with a relatively abundant supply of available 
moisture in the surface 3 to 6 feet of soil after the rainy 
period, which comes in winter in the Colorado Desert 
and both in winter and summer east of this region. 
In the early spring in the Colorado Desert the plants 
are covered with bright yellow flowers. During sum¬ 
mer and autumn the plants retain their leaves but 
present a brownish appearance and remain in a con¬ 
dition of drought dormancy. This type indicates a 
relatively alkali-free soil. In respect to soil and alkali 
conditions it is similar to the sagebrush of the north 
desert shrub, and like the sagebrush reaches its beet 
development on the alluvial fans which are often com¬ 
posed of coarse sand and gravel. In the eastern part of 
its range, under much heavier rainfall, it often indi¬ 
cates a very shallow soil and caliche. 
In portions of Arizona, New Mexico, and Texas creo¬ 
sote bush forms a scattered growth over a relatively 
pure grassland sod. Such areas constitute a transition 
from the southern desert shrub to the mesquite grass or 
desert grassland. 
Creosote bush-bur sage.- —-Above the areas of pure 
creosote bush in the Colorado Desert there may be dis¬ 
tinguished a zone of varying width characterized by 
a mixture of the dark lacquer-leaved creosote bush and 
the low, light-gray bur sage ( Franseria dumosa or F. 
deltoides). This type is not sharply differentiated 
from the yucca-cactus type. 
Black brush. —In portions of Arizona, New Mexico, 
and Texas black brush ( Flourensia eernua) constitutes 
the chief component of the vegetation. It lies either 
above or below the grassland, and occurs only on the 
better, deeper soils in the creosote-bush areas. 
Yucca-cactus. —Lying above the creosote-bush zone 
there may be distinguished a broad zone made up 
largely of yuccas, century plants, cacti, palo verde, and 
related plants. It is varied in appearance and in bo¬ 
tanical composition, and is characterized almost 
throughout its range by a greater mixture of species 
than is either the desert saltbush or creosote bush. For 
the most part it is found on the relatively rapidly 
eroding hills and ridges, the rough slopes, and low 
mountains of the southern desert region. Only rarely 
does it push down over the level stretches of the valleys, 
but reaches its lowest extension along the washes. Al¬ 
though the botanical composition varies considerably, 
this zone is set off sharply from all the other desert 
areas by the abundance of the yucca-like plants and 
cacti which here become prominent features of the 
vegetation. Very little of the land occupied by this 
type of vegetation is suitable for agriculture, and the 
grazing value of the natural vegetation is slight, al¬ 
though during periods of extreme drought cattle are 
able to subsist upon the relatively unedible plants 
which characterize this vegetation unit. 
Yuccctr-cholla. —At higher elevations on the west and 
north side of the Colorado Desert, Mohave yucca 
{Yucca mohavensis) and cacti {Ferocactus acanthoides, 
Opu/ntia bigelovii , and Opuntia acanthocarpa) , together 
with shrubs of bur sage {Franseria dumosa) and 
encelia {Encelia farinosa) constitute the major portion 
of the plant cover. 
