A berm is an elongated mound of soil, used like a large planting bed. It can offer a solution to improve drainage and open up a new area to add some of your favorite plants. Often, they are constructed around the edge of the lawn as a way to frame the yard with a colorful planting of flowering perennials or if more privacy is needed, a mixed hedge of shrubs and trees. They are best used for dividing two distinct areas of the landscape, such as a border along a property line.
Determine the location and shape of the berm, using curving, organic shapes. Build your berm at the edge of a garden area, not through it.
Mark the center line of the berm with wooden stakes. Remove any existing sod or other vegetation from the area.
Pile soil along the line formed by the wooden stakes. Excavate soil from the area adjacent to the berm or from another part of your property or purchase topsoil. Break up any heavy clods of dirt to create the loose, friable soil. Remove any existing vegetation in the soil as you add it, including roots.
Incorporate 1 wheelbarrow load of compost for every 4 loads of soil. Mix the compost thoroughly with the native soil as you form the berm.
Spread the soil in the general shape of the berm and grade it smooth, using a hard metal rake. The sides should taper gradually to blend in with the surrounding soil level on all sides. Pull out the stakes once you have the basic shape in place.
Spread mulch over the surface to protect the soil from erosion and moisture loss. You may choose to plant immediately or wait until you are ready for another project.