James Feucht, Ph.D. Colorado State University Cooperative Extension landscape plants specialist
The old-fashioned rock garden has become a new-fangled idea.
Colorful and easy on the water bill, rock gardens can be a good alternative to moisture-loving bluegrass lawn.
The ideal location for a rock garden is a natural slope or terrace, often found at the side or rear of split-level houses. By bringing in soil and other materials, you also can create rock gardens in other areas of the yard.
Following are some pointers to help you create an attractive, water-saving rock garden.
Use rocks of one geological type. Ideal in Colorado is native granite covered with lichens. This is known as moss rock.
An effective rock garden will incorporate a lot of large rocks, some weighing 200 pounds or more. Rocks of this size are available from nurserymen, landscape contractors and rock dealers.
Position rocks in a natural way, following the grain of the rock. Set into the ground so at least one-third of the rock is buried. Place to expose as much lichen as possible and to control soil erosion between rocks. Create soil pockets between stones for the placement of various-sized plants.
Plant a variety of species in the rock garden. Repeat some species several times to make the garden look natural. Most plants for rock gardens spread readily, so take care not to overplant.
Annuals and perennials are suitable for rock gardens. Initially, you may want to supplement with annuals, until perennials fill in.
Two large plant groups, the sedums and sempervivums (hen and chicks) provide numerous rock garden species. Among the better sedums are the yellow-flowered golden stonecrop and Sedum hybridum. For white flowers, try Sedum album. In poor soils, this particular species usually displays a pleasant bronze foliage. For light pink flowers, try Sedum spectabilis `autumn joy.'
Among other good rock garden plants that will tolerate prolonged dry periods are the alpine stonecrest, goldentuft alyssum, alpine rockcress, cottage pinks and thrift (Armeria).
In a large rock garden, you may want to consider some of the summer shrubs such as cinquefoil, prostrate junipers and littleleaf peashrub. The latter may be in short supply locally.
Before creating a rock garden, consider the time you'll have to maintain it. Rock gardens can be labor intensive, with weed control the biggest problem.
For a fact sheet about rock gardens, contact your local office of Colorado State University Cooperative Extension.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010