This is a classic picture of the high desert at about 4,00 feet:
The gray bushes are sage. You can see a lot of the lower yellow grasses that Jerry wrote about. The larger tree is a Pinyon Pine and the large bushes are Mesquite. You can also see how the desert goes from the mountain rainge to a basin and then up to another mountain range again. This is really typical of the basin and range high desert. The far desert tends to look mostly yellow with a few green splotches. The distant mountain range is fairly barren until you get up to about 4,00 feet when the Pinyon Pine start to dominate and makes the top parts of the mountain look fairly green.
Modeling the high desert is quite a complex undertaking since you have not only the plants of the desert but the changes of plants with altitude also. If you really want to make a believable layout in the desert, you need lots of land too. The railroads were tiny black scars in an otherwise massive scene.