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A backyard shrub island berm is a raised mound of soil that is planted with shrubs and other plants. It offers several benefits for your outdoor space.
1. Privacy: The shrubs on the berm can create a natural barrier, providing privacy from neighbors or nearby roads.
2. Visual Interest: The varying heights and textures of the shrubs add depth and visual appeal to your backyard, enhancing its overall aesthetic.
3. Noise Reduction: The dense foliage of the shrubs helps to absorb and deflect sound, reducing noise pollution from surrounding areas.
4. Soil Erosion Prevention: The raised mound structure of the berm helps to prevent soil erosion, especially on sloped landscapes.
To build your own backyard shrub island berm, follow these steps:
1. Choose the location and size of the berm.
2. Mark the boundaries and shape of the berm.
3. Excavate the area within the marked boundaries.
4. Build up the berm with layers of soil, compost, and organic matter.
5. Select and plant shrubs and other plants on the berm.
6. Mulch the area and water the plants regularly.
7. Maintain the berm by trimming and pruning the shrubs as needed.
A “shrub island” refers to a cluster of shrubs planted in the center of a lawn instead of shrubbery planted around the edges of a yard or as a hedge. A shrub island can be part of a regular garden bed planted at the same level as the surrounding landscape, planted in a raised bed, or on a berm.
What is a Berm and Why Should I Create One?
A berm is a mound, ridge, or elevated area made with soil or stone. A berm is distinct from a raised bed because it usually lacks a surrounding wall or other structure, and it has a gradual, rather than steep, change in elevation.
There are several reasons why constructing a berm can be beneficial. A berm can redirect water flow, draw attention to or away from specific areas, add elevation to a flat yard, or raise plants above waterlogged areas. When topped with trees or shrubs, a berm can provide privacy, reduce noise and light pollution. Alternatively, a berm can serve as a convenient solution for using excavated dirt when building a patio or sidewalk. A berm is an ideal location for planting various shrubs to create a shrub island.
Berms Control Water Runoff
If you have a yard with a steep slope in an area with heavy rainfall, you might want to construct a berm to manage water runoff and direct it away from your home.
Position an outlet from the berm towards a swale to channel water away from structures. When the swale is excavated, a combination of a berm and a swale (a depression for directing water flow) provides materials for constructing the raised berm. A series of berms arranged along a hillside creates multiple points for slowing down water flow. The berm itself can be planted with plants, shrubs, or trees, and the concave area of the berm can be planted with water-loving plants.
In arid climates, berms slow down runoff from heavy rainfall and allow more moisture to penetrate the soil while also preventing erosion. A crescent-shaped berm, with the open side facing uphill, can retain water and sediment, enabling gradual absorption of the water and preventing the sediment from flowing into storm drains, streams, or lakes. Trees and shrubs can be planted in the concave area of the berm to take advantage of the additional water supply.
To Enhance the Visual Appeal of Your Yard
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We Are Found Home Design
Berms are primarily used to add visual interest by transforming a flat space into an undulating one. A common place to encounter berms is on a golf course. If you have ever played golf, you can imagine how a course with undulating terrain filled with numerous berms is more visually captivating than a flat course. Since many yards are completely level, even a small berm can introduce interest and dimension. Combining berms and garden beds adds texture and height to any flat yard.
Privacy, Light, and Sound Control
It’s unlikely that you will construct tall embankments for privacy purposes, but even a small berm can increase the privacy of your yard. A berm with dense shrubbery on top is an excellent way to enhance privacy. For year-round privacy, consider using evergreen shrubs and trees or a short fence along the top of the berm. In areas where fence height is restricted, a 6- or 12-inch-tall berm with a fence on top can provide a little extra privacy. Berms and evergreens can also serve as barriers against headlights and street noise.
Extending the Growing Season
In colder climates, a berm can create a slightly warmer growing area. The amount of heat absorbed from the sun depends on the angle of the exposed area. The southern face of a berm absorbs more heat due to its angled surface, allowing for earlier blooming of spring bulbs. By creating a protected area with a crescent-shaped berm, you can grow shrubs or perennials that are typically not suitable for your hardiness zone.
Berm Design
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Karen Ruth
A berm doesn’t have to be a massive earthwork; it can be as simple as a 3- to 4-inch elevation rise from the surrounding areas. Instead of constructing a single oval-shaped berm, consider using sinuous shapes, crescent shapes, or repeating and staggered small berms. Curved and asymmetrical shapes are generally more visually appealing than square shapes, and placing the highest point of the berm slightly off-center gives it a more natural look. Plant vegetation on the berms in a way that progresses from shorter to taller as you move up the slope, which helps draw the eye upward.
Shrub Island Design
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Land Designs Unlimited LLC
Before constructing the berm, consider which shrubs you want to plant on it. If the shrub island is purely for visual interest, you can opt for a monochromatic look with all the same color or shape, or you can choose a mixed look. A monochromatic or mass planting style can create a more modern aesthetic that suits a less natural-looking berm.
For a more natural look, mix different shapes, sizes, and colors of shrubs. Incorporate deciduous shrubs (which shed their leaves in the fall) with evergreen shrubs (which retain their leaves year-round). For example, a weeping blue spruce has a columnar shape with drooping branches, a blue color, and maintains its needles throughout the year. This type of shrub can be planted at the top of the berm. Mix it with a rounder shrub and a creeping deciduous shrub that hangs over a flat boulder below. Shape the berm to complement the shrubs you will be planting and any decorative elements you will be adding.
When creating a shrub island, it is important to consider the mature size of the shrubs you are selecting. Although the shrubs may start out small, they will eventually fill in the empty spaces as they grow. Keep in mind that shrubs labeled as “dwarf” are still relatively large compared to their standard size. Be sure to take note of the mature height and spread, which could be up to 10 or 15 feet. One common mistake is planting shrubs and trees too close together, causing overcrowding as they mature. If you prefer to eliminate empty spaces, you can fill them with perennial or annual plants until the shrubs reach their full size.
Factors to Consider When Constructing a Landscape Berm
Choose a location for the berm and outline the shape using a rope or hose. It is recommended to start small, as even a small berm requires a significant amount of material. This is why many landscapers build berms in conjunction with projects that involve soil removal, such as patios, sidewalks, or swimming pools. Here are some considerations to keep in mind:
- Water runoff – the berm should be positioned uphill.
- Sun exposure – the berm should face south for warmer temperatures, or north/east for cooler temperatures.
- Sight lines – the berm should distract from undesirable views and direct attention towards desirable views.
- Shade – trees and shrubs planted on the berm should provide desired shade.
- Prevailing wind direction – the berm and plantings should slow down cold winter winds, while still allowing cooling summer breezes.
Berms have a more appealing appearance when they have curvy shapes and gradual slopes. A steeply rising berm can lead to erosion problems and be difficult to maintain. Ideally, a berm should be at least four times wider than its height, and five or six times longer. For example, an 8-inch-high berm should be at least 32 inches wide and 40 inches long.
Steps to Construct a Landscape Berm
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Supersmario/iStock/GettyImages
Follow these step-by-step instructions to build your own landscape berm:
- Once you have determined the location and shape of the berm, remove the existing vegetation, such as sod, from the area and dispose of it.
- Remove the topsoil from the berm area and set it aside. If you are creating a large berm, use coarser materials for the lower layers, as quality topsoil is only needed for the top 8 to 12 inches.
- Fill the majority of the berm with materials like rocks, concrete chunks, or less desirable soil, except in areas where trees and shrubs will be planted. Avoid using toxic materials like asphalt or railroad ties, as well as wood or construction debris that will decompose and cause uneven sinking. Build up the fill to a level slightly below the desired final height to allow for the replacement of topsoil.
- Water the berm to encourage the materials to settle and fill in any gaps before adding the topsoil.
- Adjust the size and shape of the berm as desired, and then return the topsoil to the top of the berm. It is best to create a gradual transition from the surrounding areas to the berm.
How to Plant a Shrub Island on the Berm
Plant the berm with the grasses, plants, shrubs, or trees you have selected. Follow the planting instructions provided on the plant tag. Here are some general guidelines for planting a shrub island:
- Make a hole that is only as deep as the container, but 2 to 3 times wider.
- Put the shrub in the hole while it is still in the pot. The level of dirt in the pot should be the same as the dirt around it. Add or remove dirt if necessary.
- Take the shrub out of the pot by cutting down the sides of the pot. Position the shrub in the hole with the best side facing out. Fill the hole with soil, then water and mulch the shrub.
- Add occasional boulders or artistic features on the berm to attract attention and fill visual space until the plants grow.
- Use shredded or large chip mulch that won’t easily wash away for mulching.
- Plan to water the shrubs on top of the berm more, as water will flow off the top, resulting in less moisture for those plants compared to the ones around the perimeter.
- Water new shrubs and trees daily for the first two weeks, every other day for the next 12 weeks, and then weekly for the following year.
- Consult the plant tags, the grower’s website, or other sources for specific pruning instructions for your chosen shrubs. Many shrubs require regular pruning to maintain their appearance.
