The soil in a rock garden should be well drained with only a moderate amount of humus and compost. Most rock garden plants do not like rich soil or heavy fertilization. Well-rotted manure, worked around the crown of plants in early spring is sufficient feeding for the growing season. Occasionally pockets of soil may settle or wash away so plan for periodic refreshing of soil.

The most important design consideration, when planning one of these miniature landscapes is scale. Small plants blend with small stones while slightly larger ones compliment bigger rocks. Consider using a mixture of evergreens, deciduous shrubs, bulbs, perennials and annuals. The best arrangement will look as if nature had a hand in its creation so avoid straight lines, plant multiples and vary the coupling or marriages of plant combinations. Stranding an occasional plant away from its group will help give a feel as though it has been swept away and a new group or colony is developing. Although rock gardens are traditionally thought of as a solution for slopes in full sun, an east or west exposure can provide a respite from all day sun which most plants can appreciate.

Good rock garden plants are drought resistant once they are established, making them choice candidates for hot dry sunny areas especially slopes and shallow ground but it doesn't mean they never need water. They do need occasional watering especially if there has been a long hot dry spell. Crevices around rocks provide planting space and mulching helps control weeds and keep the soil cooler but keep in mind rocks can hold heat, and open area can become dry quickly.

Marriage on the Rocks
By MaryAnn FinkPublished In: The St. Louis Post-Dispatch

Do you feel like a walk in your yard is like a hike up a miniature mountain slope? Is the rugged terrain strewn with jagged rocks? Is a stroll through your garden like visiting an ancient ruin complete with enough rocks to twist an ankle? Turn this rocky road into a perfect setting for the ultimate in "matchmaking." Some plants may offer a quick satisfying solution for poor rocky soil. Select an area in your landscape to truly become a rock garden. This low cost solution is an appealing option when there is no space to support a more typical garden. This is an opportunity to "partner" great plant combinations. Many of these "happy couples" would become easily overlooked or lost in more typical gardens.

Rock gardens require a minimum of work. They require occasional watering once established and are perfect solutions for a hillside or terraced wall areas. Rocks, purchased or on hand, should provide the basic frame work of the rock garden's design. If you don't have a rocky site already, collecting and creating a rock garden feature can be an adventure and a way to build memories for your family. Collecting and placing rocks can be fun, but always be sure to get permission from property owners before collecting rocks. Whether collecting rocks that have surfaced in your own yard or out scouting, you should gather just a few at a time to avoid a back breaking experience. Choose rocks with character - angular shapes, cracks, crevices or interesting imprints. Observe natural outcrops along the highway and hillsides and try to copy the look on a miniature scale. Group small rocks together to give the impression of larger masses worn away by time and weathering. Medium stones should be used in groups of two or three. Bury large boulders halfway into the ground for stability. Using rocks native to your area and limiting the number of different kinds of rocks in the garden gives a more natural look. Limestone, sandstone and fieldstone are typically available. You may be able to purchase large rocks and boulders at your local garden center and nursery. Many landscape centers that deal with stone will offer delivery and placement.

Once you have the bed rock, consider the plants you may want to investigate for your rock garden such as old time favorite Hens and Chicks (Sempervivums species). There are a great number of plants loosely grouped together as succulents. They have a wide variety of different shapes, color and textures that will add overall interest to your design. They are best known for their ability to store moisture in their juicy thick leaves. They are easy to grow as long as they have quick drainage. Wet can be fatal to these cactus-like plants. Some succulents are tender and may need to spend the winter indoors but several are perfectly hardy to USDA Zone 4. Most die back to the ground and reemerge in the spring but a few are evergreen or only have a very brief period of dormancy.

Some other reliable plants for rock gardens in USDA Zone 5 and 6 include small shrubs such as 'Crimson Pigmy' Barberry (Berberis thunbergii var atropurpurea 'Crimson Pigmy'). This is a compact fine texture shrub with dark burgundy foliage and stiff stems. Summersweet "Hummingbird" ( Clethra alnifolia 'Hummingbird') grows to only three feet with a profusion of white fragrant flowers. It can look quite at home in a rock garden but prefers not to dry out completely. Deutzia gracilis 'Nikko' has a gentle sprawling habit barely achieving one foot in height with white flowers in early spring. For a perfect wedding of perennials in your rock garden, try Geranium sanguineum var. striatum "Lancaster" with Veronica spicata "Red Fox." The hardy geranium develops a spreading mound of finely cut leaves with many bright pink flowers with dark pink stamens in mid-spring. The Veronica's rosy spikes match the deep pink stamens of the geranium blossoms. The geranium's foliage is an added bonus when it turns red in the autumn.

Strawberry plants make a great ground cover. They can tolerate shallow soil but not extreme drought. This means more care, but try some of the new strawberry hybrids such as Fragaria x "Lipstick" or "Pink Panda"paired with the sometimes rambunctious double flowering buttercups (Ranunculus acris 'Flora Pleno'). The Buttercup family is notorious for their vigor and it can take some effort to keep them in check. This one spreads slower and the combination is a "marriage made in heaven" with the charming chubby pink petals and the yellow stamens of "Pink Panda" or "Lipstick." Talinum teretifolium is a petite native plant which provides tiny starry flowers for a long season of interest on tufts of fine green foliage. Its delicate look is quite deceiving as it can reseed profusely when happy.

Add small bulbs such as snowdrops (Galanthus nivalis) miniature daffodil 'Tete-a-Tete' (Narcissus cyclamineus "Tete Tete" ) and botanical tulips. Try several of the ornamental onions or chives ( Allium). Annuals of small stature such as the new more compact varieties of Lantana (Lantana camara) "Lucky" series, Floss Flower (Ageratum houstonianum), Globe amaranth 'Buddy' or 'Strawberry Fields' (Gomphrena globosa) and Melapodium 'Derby' (Melapodium paludosum) can give the summer season a color boost.

The extensive array of plants to choose from for this backyard solution will help you decide which way to go if you find yourself on this type of "rocky ground."