Garden berms are mounds of soil designed to support plant life. The raised structure of the berm adds definition to planted areas. Build a garden berm into your landscape to create a focal point.
Supplies:
Hose
Landscape paint
Shovel
Gravel
Compostable material
Top soil
Plants and mulch
Determine the Slope
The top of a berm is referred to as the crown. The crown of a well shaped berm is off center, along one side of the berm. The slope of the berm should be approximately four times longer than the berm is high.
For example, the crown of a garden berm may be 1 foot in height. The slope, then should measure approximately 4 feet in length, sloping downward in a gradual fashion. Add niches or steps to create a tiered appeal. Your plantings, then, will create a visual pattern, giving the berm more appeal.
Prepare the Site
Use a garden hose to lay out the shape of your berm in the intended location. For a more formal garden berm, keep the shape geometric, such as an elongated oval. A more organic shape provides a more relaxed and informal appeal.
Mark the shape with landscape spray paint. Lay out two large tarps for the excavated soil.
Use a shovel to remove the existing grass and its root systems from the area. Toss the grassy soil onto one tarp. Dig down another 3-to-4 inches, tossing that soil onto the other tarp.
Fill in the Hole
Line the excavated area with landscape fabric, allowing an overlap around the edge of approximately 6 inches. Lay down a 2-inch layer of gravel to aid with drainage. Add another layer of compostable materials such as a mixture of straw, wood chips and shredded newspaper. Add a layer of the excavated soil -not the grassy soil- to the hole.
Continue to build up the berm using compostable materials and excavated soil until the berm is approximately two thirds of the intended height. Lightly spray the filler with water as you go to aid in shaping the materials, creating the sloped sides of the berm.
Add the Topsoil and Border
Spray the filler and pat down with the flat side of a shovel. Add a layer of topsoil and turn the topsoil into the first 2 inches of filler. Spray with water and add another layer of topsoil. Spray lightly and shape.
You should have a well shaped mound sloping gently outward into the landscape. Create a border around the mound using rock, bricks or other building material of your choice. Place the border on the landscape fabric and cut away the excess. If you don’t want a border, cut the fabric back to the edge of your berm.
Plant and Mulch
Allow five to seven days for the materials in your berm to settle before adding plants. If the soil is “slipping” add a bit of crushed gravel for added support. When all the plants are in, add a 2-inch layer of mulch.
Renew the topsoil every season by turning in compost and adding a new layer of mulch.
Resources:
University of Minnesota
Further Reading:
Seven Essential Herbs for the Garden
What to Plant to Prevent Soil Erosion
How to Prune Your Rosemary Plants
