| If you are looking for something to stay green then forget about any moss for your area. Even the desert mosses go dormant in summer and turn brown to black in color. You may have to settle for a non-moss plant if you want a green cover plant. Sagina or a Sedum might be more suitable to your requirements. |
Here is a link that might be useful: Marlays Garden with a tiny sedum
| You may want to check out Grimmia as it is a desert plant but probably in the mountains where it is cooler. |
Here is a link that might be useful: USDA section on Grimmia species