There are two basic rock garden landscapes in nature:
Those developing on mountains or in desert areas: the vegetation is low, the plants creep and show a tendency of growing close to the ground. The environmental conditions, the wind and the sun, are harsh and require tough plants, species that will be able to withstand adversities. In this case, you must choose drought-resistant plants, such as agave, Texas lantana, desert willow, lamb’s ears, sedum (or stonecrop), etc;
Those developing in deep-shaded slopes and ravines, perhaps by the edge of a creek or some kind of water stream: these are plants that can grow well without ample sunlight and can tolerate moisture, such as ferns, which are also very decorative and give a forest-like image to your garden.