Ask Mr. Smarty Plants

From this USDA Plant Profile map, you will see that Prunus caroliniana (Cherry laurel) does not grow natively in Nevada at all. This is probably your first clue to the answer to your problem. The second clue is in this section on Growing Conditions from our website page on this plant:

"Water Use: Medium
Light Requirement: Sun , Part Shade
Soil Moisture: Moist
Cold Tolerant: yes
Soil Description: Moist, deep, loamy, well-drained soils. Clay Loam, Medium Loam, Sandy Loam, Sandy
Conditions Comments: Likes the moist, well-drained soils of its natural range. Prolonged saturation can cause root rot, particularly in clay soils. Shallow, nutrient-poor, rocky soils can cause chlorosis and heat stress."

We would guess that you are trying to grow a plant that needs acidic soils in alkaline soils, and that your environment is causing chlorosis and heat stress. There is very little you can do to force a plant to grow where it does not belong, but you might try mulching the trees with a good quality shredded bark mulch. This will protect the roots from extremes of heat and cold and, as it decomposes, it will slowly add a little acidity and the possibility of better drainage to the soil. In terms of water each season, that depends more on whether the trees are better established or relatively new in the ground. If you want to try to maintain the trees instead of replacing them, we would suggest that you water at least once a week by sticking a hose down in the soil and letting it dribble slowly until water appears on the surface.