Simply placing a rock garden's stones on the ground isn't good enough. In order to create a suitable root run for accent plants and to hold the rocks firmly in place, ensure that one-third to one-half of each stone is below the soil's surface. Dig a hole the appropriate size and shape for every rock, situate each rock in its hole and then surround the base of each rock with the soil you removed to create the holes. Despite their weight, rocks may not stay in place if one-third to one-half of their height isn't below the soil surface, particularly when they are placed on uneven ground where rain runoff may erode the soil and allow them to shift.
Drain the Rain
Because standing water isn't desirable in a rock garden, creating sufficient drainage in the area is crucial. Standing water can drown accent plants, cause root rot and attract undesirable insects such as mosquitoes. Set a layer of coarse stones in the bottom of the garden before you put the featured rocks in place, and cover the coarse stone layer with sandy soil to create proper drainage. The coarse stones provide drainage space, and the sandy soil soaks up excess water.
Installing several perennials among the rocks in the garden ensures that you have plants that return year after year and cuts down on garden maintenance. Plant options for rock gardens include evergreen candytuft (Iberis sempervirens), hardy in U.S. Department of Agriculture (USDA) plant hardiness zones 5 through 9. It features deep-green leaves, snowy white flowers and grows 6 to 12 inches tall. If you prefer a burst of pink blooms on a plant that tolerates dry soil well and grows to 6 to 12 inches tall, then opt for sea thrift (Armeria maritima), hardy in USDA zones 4 through 8.
Succulents are also perennials suitable for a rock garden, and their fleshy leaves store water for future use. One succulent is house leek (Sempervivum tectorum), also known as hens-and-chicks. Hardy in USDA zones 3 through 8, it produces reddish purple flowers during June and July and thrives in rocky soil and dry conditions. Stonecrop (Sedum "Autumn Joy"), another succulent, is hardy in USDA zones 3 through 11, attracts butterflies, grows to a height of 1 to 3 feet and pairs well with ornamental grass for a natural appearance in a rock garden.