Many of the world's most scenic areas feature a combination of wild flowers and trees with outcroppings of rock. Japanese garden designers have long cultivated the art of using native plants with carefully placed boulders and stones. In North America, the plants may be different, and the ecosystems vary from rainforest to desert, but the combination of rock and native plants is still a compelling mix.
Look around at the wild areas near your garden. This is your inspiration. Yes, there are both shady areas and drier, sunnier spots, but they work in harmony, instead of clashing. Introduce a "native" from an ecosystem 100 miles away and chances are it will look out of place.
Japanese designers spent years wandering through forests and up mountains, observing how nature puts things together. As much as possible, do the same. If you live near a desert, hike through it, gathering ideas, noticing in particular the kinds of rocks, how they lie, how they are found naturally, how plants grow around them.
Boulders are expensive, but even a few add a sense of depth to a garden that cannot be duplicated. Setting them properly, so they look as if they'd been there for hundreds of years, is essential. What do you see at the edge of a rocky stream? Half-buried boulders and stones. How are rocks found on a mountain slope? Again, half, perhaps even two-thirds buried. Spend the time to get placement right and your design is half-finished.
Manipulating Moods with Rocks
Upright, vertical slabs of rock give a sense of excitement. Horizontal, flat ones are restful. Combine rounded and broken stones for contrast.
Trees & Shrubs
What's the most ornamental tree that grows in your area? Natives can be spindly or weedy, but usually there are true ornamentals in every ecosystem. Place one next to a boulder and you have an instant focal point. Or make a small grove of five to one side of a dry stream bed, a rocky re-creation of a creek complete with twists and turns, but no water.
Shrubs are often found as a middle layer of plants in a forest, and even a few placed beneath a tree will give the effect of a natural landscape. Again, choose the most ornamental, especially in the most visible sections of the garden, leaving the less attractive ones for filling in back corners.
Natural areas often have just a few species in bloom at any one time, but they occur in such great numbers that the effect is stunning. Imitate this in your own garden by settling on a few species that grow well for you and then planting lots, creating drifts of California poppies, for instance, or trilliums. Try a few first, and then, if they settle in and grow vigorously, plant as many as you can.