You can use boulder landscaping to do things you couldn’t do with rocks. The first idea that comes to mind is a retaining wall. The sheer massiveness and weight of the boulders can easily hold back tons of soggy dirt. Applying geotextile fabric and gravel between the rocks and dirt will prevent the dirt from slowly seeping through the boulders while letting the water drain.
Steps are also a good idea. When using a natural material such as boulders to build steps, it may be a good idea not to use perfectly straight lines. A slight curve, or even multiple curves, may be better adapted to this style.
Boulder landscaping can also be used to create a pond if you have a stream running down your yard. Using geotextile fabric will prevent the water from seeping into the ground and slow the flow of water going through the boulders. Be careful though not to use to much fabric, because it may catch all the sand carried by the stream and turn your pond into a puddle of mud in a matter of months. Some people make holes in the fabric to let the water flow faster and to give an escape route for the grains of sand flowing down with the water. Use rocks to stabilize the fabric so as to ensure it doesn’t move as the water goes through the pond. If you plan to grow plants in such a pond, you should be careful to choose plants that will not pose a problem to the ecosystems downstream. Aggressive non native plants have been known to invade streams and choke out native vegetation.
Boulder landscaping in the garden
But boulders can also be used simply in rock gardens. You can use a few boulders in a smaller garden, or many of them in a larger one. You can use boulders to build a retaining wall and then more boulders to create a garden adjacent to the wall. Shop around when getting your boulders. You should be able to find various types of boulders with different colors and shapes. As in a rock garden, boulders should be chosen for their esthetic qualities.
The big problem with boulders is their size and weight. You need machinery just to move them, so playing around with them trying to find the best location may be a bit difficult.
Have you considered all the possibilities? There are some landscaping ideas you may not have thought of.