There is a reason they are called rock gardens. They are primarily rocks. Rock gardens are low maintenance and easy care. They are also referred to as desert gardens, xeriscape or alpine gardens. They require little in the way of soil, mulches or water. Rock gardens require certain plants to survive its harsh environment.
If you live in high altitudes then alpine plants would be suited to your climate. In lower hotter regions cacti would be more appropriate. Here are few points to consider when building your rock garden. Lay a heavy layer of cardboard down in your rock garden area as this will smother all the grass seed that may be dormant in your soil. Place your rocks where you want them. Go the to local landscaper and choose the rocks you want to make your garden.Choose a variety of sizes, shapes and colors that would be attractive with the color of your house. Add your garden soil with several bags of sand included.
Now arrange your plants where you would like them to live. Try several arrangements until you find the one that appeals to you the most. Make sure to vary the rock colors as well as the plant colors. A landscape professional can help you with your choices.
I have several personal favorite plants for the rock garden. Hen and chicks, cosmos, coreopsis, blanket flower, mexican marigold, indian paint brush, native grasses, lamb's ear and mullein just to name a few. These are extremely drought resistant, low maintenance and shine brightly in hot dry weather. Scotch moss and thyme grow into the crevices and look very attractive. Sweet william, candytuft, carpet bugle, rock cress, serbian bellflower and daylilies are excellent choices as well.
Yarrows and coneflowers are very hardy and come in a variety of colors attracting butterflies and bees. Primrose, phlox, iris, sedum, butterfly plant and humming bird plants are more choices worth considering. Daisies and baskets of gold make a stunning display against red sandstone. Pine needles and wood bark make good mulches for plants in very cold or very warm climes. River rocks, pebbles, sand all work to hold your soil in place. These allow the oxygen and water to move freely into the soil.