1. Moisture: Mosses thrive in damp environments. Rocks, especially those in shaded or humid areas, can retain moisture, providing a suitable habitat for moss growth.

2. Surface Texture: The rough, porous surface of rocks provides a good anchor for moss rhizoids, which are root-like structures that help them attach to surfaces.

3. Nutrients: Mosses are able to absorb nutrients directly from the air and rainwater. Rocks, over time, may accumulate organic matter and mineral deposits that provide a source of nutrients for the moss.

4. Light: While mosses don't need a lot of light, they do need some to photosynthesize. Rocks can provide a stable platform for moss growth in shaded areas where other plants might struggle.

5. Competition: Moss can outcompete other plants for resources in harsh environments like rocky surfaces. Their ability to survive with limited nutrients and water makes them well-suited for these conditions.

6. Symbiosis: Some mosses form symbiotic relationships with other organisms, such as fungi, which can help them access nutrients and moisture.

7. Spore dispersal: Moss spores are easily dispersed by wind and water, allowing them to colonize new areas, including rocky surfaces.

It's important to note that not all rocks are suitable for moss growth. Factors like rock type, exposure to sunlight, and overall environmental conditions can affect moss growth.