There are several places in the world with climate similar to that of the Santa Clara Valley. There are also a few places with similar soil; and even a few with similar water quality. However, it is rare to find places which are remote from each other with many similar qualities. What can be grown here and how it is grown is specific to this area.

Plant species best suited to gardening which are not native are imported from places with similar climate, such as Italy, Algeria, South Africa and Australia. Because many do not originate in areas with similar soil types, special accommodations are often necessary. For example, many cedars from the Mediterranean thrive in the climate of the Santa Clara Valley. However, they often experience problems with drainage as they prefer rocky “soil” similar to that of their native regions.

Fortunately, mild climates, such as ours, are also more conducive to gardening with not so well suited species. With soil modification and proper irrigation, plant species which would not normally grow here may be used successfully, although not as commonly. Even species from high mountains or desert areas may be imported for garden use.

“Ornamentals” are not commonly derived from such harsh environment because such species are often too specialized to be of ornamental or functional value. Many are too small or grow too slowly to be effective in typical landscapes. Garden enthusiasts who enjoy collecting these unusual species often construct rock gardens to keep them happy and to display them separately from other styles of landscapes.

Rock gardens were actually developed in Europe to provide homes for unusual species, known as “Alpines” because they were collected from high elevations of the Alps. Similar gardens may also feature plants collected in moraines (glacial deposits) or scree (broken rock which accumulates at the bottom of cliffs or steep mountains).

Western (North American) rock gardens are more likely to include a wider range of plant species. Perennials from southwestern deserts or the Rocky mountains are more common than Alpines. The dryer and warmer but mild climate are also suitable for desert plants from other continents. Landscape style is also distinctively western. They may be large enough to fill an entire garden, or small enough to fit in an atrium.

It is important to remember that rock gardens are not simply constructed to landscape overly exposed areas. The worst are those between the sidewalk and street, surrounded by pavement. I find that such landscaping enhances the inhospitable nature of the space. Rather, they should be constructed where the small plants within them may be enjoyed in a more usable part of the garden. It is also important to emphasize the plants in the garden and not the rocks. Although rocks generally are used enhance the appearance of the garden, their primary function is to provide the plants with growing conditions similar to those in their respective natural environments.

One main requirement of rock gardens is very good drainage. Classic rock gardens are often planted in thin layers of loamy soil over coarse gravel or pulverized concrete. Because most plants originate in deserts or high mountains, they are accustomed to growing with minimal soil. Most rock gardens are installed with almost full sun exposure. However, there are many species conducive to rock garden culture which will tolerate some degree of shade. Planting on a slope or terraces is more effective for displaying low growing plants.

Cactus and succulents have traditionally been popular; however, many other perennials and even dwarf trees are also suitable. Light shade trees or bamboo may be included if sun exposure is too intense. In rock gardens, sculpture may be effectively displayed more appropriately than in most other styles of landscapes. Just remember that everything in the garden should be compatible. The appearance of a rock garden easily loses it’s appeal with the addition of inappropriate material.