May 24,1924 Significance of the Southwestern Desert Vegetation 773 
SEEPWEED 
TOPOGRAPHICAL CONDITIONS 
Seep weed is widely distributed and grows well both in the Great Basin area 
and in the Southwestern desert region. In the Coachella Valley seepweed 
(Dondia torreyana (S. Wats. Standi.) forms a narrow and irregular belt on the 
more level land between the desert-sage and pickleweed land (fig. 2). 
Seepweed grows in two quite distinct zones. One is on dry land, where it 
covers depressions of flat areas bordering Atriplex linearis S. Wats, or desert- 
sage. The other is on wet land (seepage land) bordering pickleweed or saltbush. 
In the Gila Valley seepweed ( Dondia intermedia (S. Wats.) Heller) occupies 
low flat areas that are poorly drained and are usually covered with water after 
a rain. This plant is quite frequent wherever the valley floor is a broad plain 
with very little slope. The pure areas are small, rarely exceeding 40 acres in 
extent, but are usually surrounded by larger areas mixed with either narrowleaf 
saltbush or a scrubby growth of desert-sage. These mixed areas are in turn 
surrounded by areas of pure narrowleaf saltbush or desert-sage. Seepweed 
also occurs in places where soil conditions and the associated plants are very 
different from those mentioned, namely, “seepage areas,” where it is found with 
pickleweed, grease wood, saltgrass, or sporobolus. These are usually strips of 
land along streams, as the Gila River or the Little Gila, or below irrigated tracts 
of land. 
Table XXV.— Comparison of spring and fall soil conditions at the same station in 
a typical area of saltbush , Chandler , Ariz. y 1915 a 
Item 
Depth 
of 
soil 
Date of collection 
Aver¬ 
age 
Date of collection 
Aver¬ 
age 
Mar. 
2e 
sample 
No. 21 
Mar. 
27 
sample 
No. 24 
Mar. 
17 ’i 
sample 
No. 4 
Oct. 5, 
sample 
No. 21 
Oct. 5, 
sample 
No. 24 
Oct. 5, 
sample 
No. 4 
Feet 
Moisture equivalent . . 
1 
' 19.4 
21.2 
20.3 
20.5 
21.4 
21.0 
2 
18.9 
20.9 
19.9 
19.2 
21.6 
20.4 
3 
18.3 
22. 5 
20.4 
19.7 
21.1 
20.4 
4 
22.9 
23.3 
23.1 
22.2 
23.6 
22.9 
Wilting coefficient 
1 
10.6 
11.5 
11.1 
11.1 
11.6 
11.4 
2 
10.3 
11.4 
10.9 
10.4 
11.7 
11.1 
3 
10.0 
12.2 
11.1 
10.7 
11.5 
11.1 
4 
12.5 
12. 7 
12.6 
12.1 
12.8 
12.5 
Moisture content above or 
1 
+14.7 
+10.0 
+12.4 
+7.4 
+6.0 
+6.7 
below wilting coefficient. 
2 
+21.0 
+15.9 
+18.5 
+11.3 
+8.5 
+9.9 
3 
+25.0 
+16.8 
+20.9 
+13.1 
+9.6 
+11.2 
4 
+21.2 
+18.2 
+19. 7 
+10.5 
+11. 8 
+11.2 
Salt content. 
1 
.45 
.75 
0.64 
.61 
.38 
.97 
1.34 
.90 
2 
.34 
.41 
.46 
.40 
1.48 
.37 
.47 
.84 
3 
.34 
.38 
.41 
.38 
.90 
.32 
.47 
.56 
4 
.33 
.37 
.35 
1.80 
.31 
.49 
.87 
HI 
a All data in this table are stated in percentages of the dry weight of the soil. 
BOTANICAL COMPOSITION 
Pure areas of seepweed, where no other plants are present are small and 
uncommon. In the Gila Valley plants of Atriplex linearis S. Wats., Atriplex 
fascicnlata S. Wats., Aster parviflorus A. Gray, or, sometimes, Plantago erecta 
Morris are mixed with the seepweed ( Dondia intermedia (S. Wats.) Heller.) How¬ 
ever, when seep weed grows on the “seepage” lands it is mixed with Allenrolfea 
occidentalis (S. Wats.) Kuntze, Sarcobatus vermiculatus (Hook.) Torr., Sporobolus 
airoides Torr., Distichlis spicata (L.) Greene, Atriplex lentiformis (Torr.), S. Wats, 
and Pluchea sericea (Nutt.) Coville. 
