Adding a Basic Berm to Your Garden

A berm is a raised mound of earth used to support plant materials like grass, flowers, shrubs and trees. Berms can provide protection from wind, screen undesirable views, add privacy, direct water drainage or make a flat yard more interesting. 

Planning a Berm

If you are using trees and shrubs, then your berm should be proportionally larger than if you are planning a rock garden or flower bed. If your berm will have grass, then it should have a gentle slope for mowing ease. Typically 1 to 4 feet in height, a berm needs to be 4 to 5 feet wide for every foot of height. 

The berm should not impede the way natural water drains from the site, unless its purpose is to improve that drainage. Also consider what mature trees or other plantings would be affected if the berm changed the natural drainage. 

Building a Berm

To build the berm, remove some soil from the surface and slightly break up the subsoil for drainage. Bring in fill soil or additional clay soil to create the height wanted. Do not use sandy soil, as it will wash away easily.

Evaluate the shape and height of the berm. If it is large, create a higher point at the back, then slope gently down for a more natural look.

Finish the project with an even 2 to 3-inch layer of top soil, incorporating any amendments and mixing the top soil layer slightly into the heavier soil beneath. Tamp it  lightly with the back of a rake and allow the berm soil to settle for at least a week before planting.