When designing a landscape, there are many things you can use to enhance its features. Something as simple as the addition of large rocks and boulders can make a flowerbed "pop". Whether you are trying to draw attention to a particular plant or section of the garden, rocks and boulders can do it. You should address the use of large rocks and boulders as you would the outline of the garden itself: Let your imagination take charge.
Mound your large rocks or boulders together in the flowerbed to create a waterfall effect. Place a water system in you garden and hide the piping in the rocks. You can then allow the water to cascade off the top of the rock pile and create a waterfall. Plant your base rocks several inches into the soil to keep them stable and give the waterfall a natural look.
Place your large rocks and boulders in an area to showcase a particular plant, such as a specimen palm tree. Plant your tree in the centre, and place your large rocks and boulders around the outside of it. Dig a hole approximately 4 to 6 inches deep to plant your rock in.
Mound your large rocks on top of each other, leaving cracks in various spots to plant small plants. When the plants begin to grow, they will cascade down the rocks. Plant your base rocks several inches into the soil to keep the rock formation natural looking and stable.
Create a berm and add extra height to it by placing large rocks and boulders across the top. You can then plant bushes or trees in the top and side sections of the berm, and they will add height as they grow. Plant your larger rocks several inches into the soil when you place them.
Build a pond area in your garden, and use the large rocks and boulders to add a natural effect. You can also have water flowing down the rocks and into the pond to keep the water at a steady level.
You probably will need people to help you move the large rocks and boulders. When placing a large rock that will be a specimen, be sure to face the rock the way you want to look at it when planting.