Designing landscape mounds & berms
A perfectly flat landscape is easy to mow but it isn’t very interesting. Build gently sloping mounds and berms to show off flowers, create a physical barrier, or even change a drainage pattern.
Ann Marie VanDerZanden is a horticulture professor at Iowa State University. She says when you’re planning the dimensions, use simple math so the berm doesn’t look like a volcano.
"The berms should be about 4-5 times as long as it is tall. In order to make them look like an actual element in the landscape rather than just kind of a high spot in the landscape, they should be probably about 18” up to about 24” tall," says VanDerZanden. "Once you get more than about two-feet, then you can start to run into some erosion issues."
Lay out the design you want with a garden hose. Crescents and curves are a lot more interesting that straight lines. Have the highest point of the berm at one end, and gradually taper it down to grade at the other end. You could also have more than one peak.
How you build and fill the berm depends on your available resources.
"People will use poor quality soils or even a little bit of construction debris, little chunks of concrete or something like that. And then I like to recommend about 6”-8” of topsoil on top of that," says VanDerZanden. "One thing that I see that people do sometimes is they don’t put the good quality soil on top. The plants need something good to grow in, otherwise they’re not going to do very well."
If you’ll be planting trees or shrubs with deep roots, she recommends building the entire structure out of good-quality soil. It’s also a good idea to cover it with mulch or plant a ground cover to control erosion.
Find more tips for building a mound or berm in your landscape
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