774 
Journal of Agricultural Research 
Vo 1. XXVIII, No. 8 
In Coachella Valley the seepweed ( Dondia torreyana (S. Wats.) Standi.), out¬ 
side of the small pure areas, mixes, on the one hand, with plants on wet saline 
land, as Distichlis spicata (L.) Greene, Allenrolfea occidentalis (S. Wats.) Kuntze, 
Atriplex lentiformis (Torr.) S. Wats, and Fluchea sericea (Nutt.) Coville, and, on 
the other hand, with plants on dry desert soil as Atriplex polycarpa (Torr.) S. Wats, 
and Atriplex canescens (Pursh) Nutt. In fact creosote bush ( Covillea glutinosa 
(Engelm.) Rydb.) and the plant groups above the creosote bush area are the only 
ones with which Dondia does not mix. Where it is near Covillea, Dondia occupies 
depressions while Covillea grows on hummocks of lighter soil. 
APPEARANCE 
In the wet (“seep”) areas, seepweed grows in dense tangled clumps with 
open spaces between the clumps, the soil being heavily crusted with salt (PI. 14, A). 
In summer the plants are very dark green, but in late fall they are tinged with red 
or purple. Still later most of the leaves are dropped. The new growth comes on 
late in spring after the creosote bush has made most of its growth. This is 
probably due to the fact that there is much more moisture for the seepweed to 
draw on later in the season and also that, due to its location, the soil does not 
become warm as soon as in the case of the creosote bush land. Wherever seep¬ 
weed areas are found on dry land the growth is usually not over 16 or 18 inches 
high, scant but quite uniform. In spring the plants are green but not as dark 
green as those on the wet areas. The plants on the dry land become tinged 
with red or purple earlier than those on the wet lands. 
PHYSICAL CONDITIONS INDICATED 
Soil Moisture 
The texture of the soil indicated by the seepweed ranges from a fine sandy 
loam to a clay loam, usually somewhat heavier than that indicated by the desert- 
sage. The amount of available water is considerably greater than on desert- 
sage soil in the spring. In the fall the soil moisture of desert-sage land is con¬ 
siderably below the wilting coefficient, but the soil moisture of the seepweed 
land is somewhat above the wilting coefficient, at least in the third and fourth 
feet (Tables XXVI and XXVII). Where the seepweed grows on seep land there 
is usually abundant soil moisture all the year. 
Salinity 
Seepweed is a good indicator of saline land. The only exception to this is that 
seepweed may, as a weed, temporarily cover land once cultivated and then 
abandoned (PI. 13, B), in which case it is not always an indicator of salinity 
(sample No. 44, Table XXVIII). Even when mixed with other plants it 
rarely fails as an indicator of high salt content of the soil (Table XXIX). In 
Tables XXVI, samples 11 and 12, and XXVII is shown the salt content on dry 
land. The first foot has a considerable salt content, at least in fall, while the 
last 3 feet are high in salt content. The salt content indicated by seepweed on 
“seep” land (PI. 13, A) is shown in Table XXVIII, all 4 feet being high in 
salt content. 
Summary of Physical Conditions 
A rank tangled growth of seepweed indicates (1) a high water table; (2) a 
high salt content, the average of the 4 feet exceeding 1 per cent, while the first 
foot may contain over 2\ per cent (sample 13, Table XXVI). 
A scant, low, uniform growth indicates (1) available water in all 4 feet in 
spring and usually some available water in the third and fourth feet in fall; (2) a 
high salt content, the average of the 4 feet ranging from 3^ per cent to 1 per cent. 
