When your trees, shrubs and small plants went into the ground in your yard, you or your landscaper wisely created a berm, or a raised mound of dirt, around the circumference of each plant to capture rainfall or your sprinkler's water shower, delivering moisture down to the roots. Right now, though, you may notice that those berms have eroded away because of the weather or been damaged by children playing in the yard, careless lawn mowing or the trampling of deer and other animals.
It's time to repair those berms so that they can deliver water for your garden investments' growth, protection and beauty.
*Creating a Berm
If no berm exists, either because of erosion or because one never was created, you'll need to make one now. Start by using a rake to clear away any leaves or mulch from beneath your plant. A debris-free surface is essential. Next, decide how big the circumference of your berm will be. A natural line may be there already from when your tree or shrub was planted. Ideally, the berm will be big enough to deliver water to the entire root system. So to be efficient and attractive, your berm might encircle your tree in a diameter of 3 or 4 feet. For shrubs, the berm could extend 6 inches or so outside the width of the plant.
According to the Urban Forest Ecosystems Institute, the height of your berm should be less than 4 inches. "Water held in a taller berm simply runs through the root ball."
Next comes choosing your berm material. You can use regular garden soil or topsoil, and the UFEI says, "It might be more appropriate to make the berm from mulch since the berm typically ends up on top of the root ball eventually. Placing soil over the root ball cuts off oxygen and water."
Using a shovel, begin digging gently around the circle where your berm will be to loosen the soil that is native to the plant's location. Use a shovel to blend in scoopfuls of new topsoil to make a mixture on the ground surface, and then use your shovel or your hands to form this soil mixture into a ring around the plant, creating a "wall" that slopes gently toward the plant. A rounded top is not efficient. Then lightly tamp down the newly created berm. Smooth out the shape using the backside of a rake until your berm appears as you want it to.
Cover any exposed soil inside the ring with a 3- to 4-inch layer of mulch to prevent the soil from drying out and eroding.
*Repairing an Existing Berm
If your berm still stands but has lessened in size or has a missing portion, refresh it by scooping fresh topsoil into the "broken" parts. At the same time, add fresh topsoil to any other sections of the ring that need extra height or width. Use your shovel or hands to shape the ring, creating an inward slope so the berm can deliver water to the plant's roots below.
At this time, water your plants and the berm with a sprinkler or with a hose on the mist setting. Forceful water can knock your berm out of shape again. Saturate the berm, and press again with your shovel to secure it into place.
Not all berms are created from soil, topsoil and mulch. Some berms can be created using rocks to aid in water retention, especially if you have a sloping yard or garden bed. Some gardeners love the look of using a ring made of layers of slate to match the slate-created border walls they have elsewhere on their properties, for example, outlining their front landscaping. When the larger rocks have been pressed into the soil, you may wish to beautify and further secure your berm's ring with river stones.