Rock gardens are effective if built on a natural slope or terrace.
Use rocks of one geological type.
Good drainage is necessary.
Plant a variety of species in the rockery.
The garden should not be larger than can be easily maintained.
A rock garden is defined as an outcropping of rocks into which a careful selection of low-growing perennials, annuals, bulbs, and shrubs are nestled. Installing a rock garden is not an easy proposition, so you might want to read about it or take a class beforehand. Or, you can observe natural rocky terrains and man-made rock gardens like those at the Denver Botanic gardens. In the meantime, there are some guidelines you can think about.
Rock gardens are a good choice for sloping sites because the angle of the slope emulates the mountainous regions and many plants traditionally used in rock gardens originate in these regions.
You also can construct a rock garden on level ground in an area that receives ample sunlight. Any turf you remove can be used as a handy base to elevate the grade but add plenty of coarse stones to provide a well-drained base on which to place a sandy soil mix and the featured rocks.
Google your local landscape material supplier to identify sources for retail landscape rock. Select rocks of the same type, but different sizes.
Generally speaking, it’s best to place the largest rocks within the soil base towards the bottom of the slope. Arrange smaller ones to give the impression that they have tumbled down. Place all rocks on their broadest side and bury them at least half-way into the finished grade.
Although installing a rock garden is a challenging task, it’s also fun, especially when it’s time to plant. The rocks provide many different niches into which carefully selected plants can grow. Large garden centers
and nurseries have a special section of rock garden plants to aid you in your decision.
The ideal location for a rock garden is a natural slope or terrace, such as those found at the side or rear of a house based on a split-level or garden-level design.
Use rocks of one geological type. A common rock in Colorado is native granite covered with lichens (moss rock). Rocks are available from nurseries, landscape contractors, and rock dealers. An effective rock garden should have several large rocks, some weighing 200 pounds or more.
Set the rock into the ground so at least one-third is buried. Place rocks in a natural way, following the grain of the rock. Position rocks to control soil erosion between rocks and to allow soil pockets of various sizes for plants. Use smaller, similar rock as a mulch. Place lichen-covered rock to expose as much of the lichen as possible.
Provide good drainage. Most plants suitable for rock gardens require a well-drained soil. For most plants, incorporate organic matter into heavier clay soils to improve texture and provide better drainage.
A rock garden should be no larger than can be easily maintained. Rock gardens have high maintenance requirements. Weed control is the biggest problem. Most rock garden plants need low to moderate watering amounts and frequency.
Plant a variety of species, repeating some species several times to make the garden look natural. Ideally, rock garden plants should spread slowly. Take care not to overplant.
Many types of plants are suitable for rock gardens. Generally, plants that are low growing and have a clumping habit are preferred. Perennial plants are most common in rock gardens, although some annuals can be used.
Here are a few suggestions to get you started, you can google for more:
Ajuga reptans, Carpet bugle, Atropurpurea, Burgundy Glow
Alyssum montanum Mountain alyssum
Arabis caucasica Snowcap’, Snowcap rockcress
Armeria maritima Sea Pink Victor Reiter
Campanula, carpatica, Carpathian harebell
Delosperma cooperi Purple ice plant
Gazania krebsiana Tanager®
Linum flavum Compactum Dwarf golden flax
Penstemon caespitosus Creeping penstemon