If you get heavy rain and flooding in your yard, you need a way to prevent mulch from washing away. Mulch washes away when rain or irrigation produces a flow of water that is too strong, or if your mulch is too light (low-density).
So, how do you prevent mulch from washing away? First, redirect the flow of rainwater from your house, and install drainage if necessary. Next, choose a heavier (high-density) material the next time you need to replace the mulch in your landscaping. Then, add edging to your landscaping to retain mulch. Finally, reduce or eliminate slopes in your landscape to keep mulch from floating away down the incline.
It will take some work to make these changes. However, it will save you time in the long run, since it can be a real pain to clean up mulch after every storm.
In this article, we’ll look at ways to prevent mulch from washing away by using drainage, heavier mulches, landscape edging, and reduced slopes.
Let’s begin.
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How to Prevent Mulch from Washing Away
There are many options to prevent mulch from washing away, but using multiple methods will yield the best results. Some ways to prevent mulch from washing away are to:
- Redirect the flow of water – if you place your downspouts strategically, you can direct water from the gutters away from mulch in your landscaping to prevent it from washing away. You can also install French drains or other drainage systems to avoid a flood of water that washes mulch away.
- Choose heavy mulch – not all mulches are created equal. Some are light (low-density), and they will float in shallow water and wash away easily. Others are heavy (high-density) and will stay put, even with a strong current of water flowing by. If you don’t want to remove the old mulch, simply wait until it decomposes and it is time to add new mulch. You can learn more about alternatives to wood mulch in my article here.
- Add Edging – edging will help to retain mulch and keep it from washing away by creating a physical barrier. However, edging can also add beauty to the landscaping in your yard. There are many edging materials to choose from, including stone, wood, plastic, and rubber.
- Reduce Slope – mulch is more likely to wash away when water carries it down a hill or any kind of slope in your yard. If you can reduce or eliminate the slope, it will be much easier to keep mulch in place.
Let’s take a closer look at these methods of preventing mulch from washing away. We’ll start with ways to redirect the flow of water.
Redirect the Flow of Water
The next time it rains and you see mulch washing away, pay attention to where it comes from. Most likely, it will come from downspouts on your house or it will run down a slope in your yard.
Making a few small changes to your gutters and downspouts is easy to do, so we’ll start there.
Gutters and Downspouts
Are the downspouts from your gutters sending water right into the mulch in your landscaping? If so, you can use downspout extensions to prevent the problem.
Choose the appropriate downspout extensions and attach them so the water flows right past the mulch. You can find downspout extensions (rigid or flexible, with or without bends) such as this one at Home Depot or this one at Lowe’s.
You also have the option of burying your downspout extensions to hide them. Just be sure to use gravel in a trench and dig so that the trench gets deeper the further you go from your house.
This will encourage the water to flow away from the foundation and from your mulch.
Drainage Systems
Is your mulch is being washed away by water from a slope or hill in your yard? If so, then it will help to install a drainage system to send the water where you want it (instead of letting it wash away your mulch).
The idea is to dig a trench and encourage water to flow into and along the trench, directing it away from your mulch. To help the water flow along, you can put a pipe in the trench.
Some drainage pipes are solid, so that the water will flow all the way through to the other end. For example, here is a solid drainage pipe made of polyethylene from Home Depot.
Other drainage pipes are perforated (they have holes), so some of the water will flow out through the pipe as it moves along. For example, here is a perforated drainage pipe from Home Depot.
If the drainage ditch will be going underneath the mulch in your landscaping, it might be better to use a solid pipe rather than a perforated one.
You can also fill a trench with gravel to allow water to slowly drain away through the rocks (as in a traditional French drain).
You can learn more about how to install a French drain in this article from Home Depot.
Choose Heavy Mulch
Using heavier (higher density) mulch may prevent it from washing away, even if you are not able to redirect water in your yard.
Lighter (lower density) types of mulch (such as pine wood chunks) tend to float in water and get washed away easily.
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What Kind of Mulch Won’t Wash Away?
Heavier mulches resist washing away, and they also last longer so that you won’t have to add new mulch so often.
Some types of heavy mulch that won’t wash away easily include:
- Gravel – choose either small or large stones, depending on the appearance you like for your landscaping. It will be nearly impossible for water to wash away larger pieces of gravel unless it is really flowing quickly. Gravel will not decompose, so you won’t need to replace it as you would with ordinary wood mulch. The only downside is that gravel is heavy to put into place – but you only have to do it once!
- Rubber Mulch – large chunks of recycled rubber may not have the nicest appearance, but they will resist washing away. They are not as dense as rocks, but they won’t float in water. Rubber chunks, like rocks, will not decompose, so you won’t need to replace this material. Rubber is a good, long-lasting alternative to gravel if you don’t want to deal with moving heavy rocks.
- Hardwood Mulch – this mulch comes from oak and other hardwoods, and it is made out of the leftovers from logging for lumber and paper production. This mulch will resist washing away, but it will naturally decompose over time, meaning it needs to be replaced every so often.
The table below gives wood densities for a sampling of tree types.
| Wood | Density (kg/m3) |
|---|---|
| Bamboo | <400 |
| Aspen | 420 |
| Yellow Pine | 420 |
| Cypress | 510 |
| Black Ash | 540 |
| American Elm | 570 |
| Birch | 670 |
| European Ash | 710 |
| Holly | 760 |
| Oak | 740 |
| Beech | up to 900 |
of various types of wood.
Shredded wood mulch is less likely to wash away or blow away than wood chips. Still, there is a downside to using finely chopped or shredded wood mulch.
Remember that fine wood mulches will decompose faster than mulch with larger chunks of wood. Decomposing wood will temporarily “tie up” nitrogen in your soil, so you will need extra nitrogen to help offset this.
Sawdust has fine particles and it breaks down fast – but it will also tie up nitrogen in the soil much sooner. Sawdust might be better used as a part of compost than as mulch – you can learn more here.
Add Edging
Even if you don’t want to change the mulch in your landscaping, you can still use edging to retain mulch and prevent it from washing away.
What Materials to Use for Edging
There are lots of materials you can use for edging to keep mulch in place, including:
- Stone
- Wood
- Plastic
- Rubber
Each of these edging materials has its own benefits and drawbacks. We’ll start with stone materials.
Stone
Stone will last a long time, since it won’t rot like wood or crack like some plastics. However, stone is the heaviest of the materials, and so it is the most difficult to install.
Also, remember that stone will never add organic material back into the soil (unlike wood, which eventually decomposes to add nutrients back to the soil).
Depending on what you have available, you can use lots of different materials for stone edging, such as:
- Bricks – made of clay, bricks are more expensive than rocks. However, they have a uniform size and shape, so they are easier to line up and stack.
- Pavers – made of concrete, pavers are less expensive than bricks, but more expensive than rocks.
- Patio Stones – these stones have an irregular shape and are harder to line up and stack to make edging to retain mulch. However, they have a nice appearance and are one option if you have some extra from a patio project.
- Rocks – you can find these for free in your garden (it seems that no matter how many rocks you pull out of the soil, there are always plenty more to be found!). Rocks can be used to build a short stone wall to keep mulch in place. If you want, you can paint them white to give them a uniform color, or leave them in their natural state.
- Concrete – you could also create custom concrete edging by putting a wooden form in place around the perimeter of the mulched area in your landscape.
Wood
Wood will decompose over time, but it is lighter and easier to work with than stone. You can use stain or paint to preserve wood edging and give it a longer life.
You can use either real wood or composite wood (a product containing a mixture of wood, plastic, and adhesive).
If you want, you can build your own custom edging with lumber. You can also keep things simple by buying pre-made modular edging, such as this edging from Lowe’s, or this composite edging kit from Gardener’s Supply Company.
You can also get a nice landscaping effect by building wood edging out of the same material that the mulch is made from. For example, you could build cedar edging to go along with cedar mulch (although this would be an expensive combination!)
(If you want to opt for cedar mulch, you can find it online from Ace Hardware).
Plastic
Plastic is a great choice for edging to retain mulch. Plastic lasts a long time, since it won’t rot like wood. Plastic is also much lighter than stone and easier to work with.
There are lots of different types of plastic available for landscape edging, with lots of different appearances.
For example, this plastic edging from Lowe’s has the appearance of wood, but won’t rot away.
On the other hand, this plastic edging from Gardener’s Supply Company has the appearance of cobblestones, but it is much lighter and easier to work with than stone.
Rubber
Rubber edging is a little more flexible than plastic, but a little bit heavier. It is long-lasting, just like stone, but it is much lighter.
You could use recycled rubber mulch edging to go along with rubber mulch for a once-and-done landscaping setup.
Here is a roll of recycled rubber edging (12 feet by 6 inches) from Gardener’s Supply Company.
Reduce the Slope
Finally, you can reduce the slope in your landscaping to prevent mulch from washing away. One way to do this is to even things out with soil and mulch.
How to Keep Mulch from Washing Away on a Slope
First, use soil to reduce the slope in your yard if possible. If you already have mulch in place, you can reduce the slope by applying mulch a little thicker in lower areas.
Then, use edging (as described above) to keep the mulch from washing away down the slope. If the slope is steep enough and the water runs fast enough, it might still be able to wash the mulch right over low edging, so make the edging taller if necessary.
Another possible solution is to use terraces. Terraces create spaces for mulch to exist where it is surrounded by barriers that make it difficult to wash it away.
Conclusion
Now you have some ideas about how to prevent mulch from washing away. You also know about some of the materials you can use for edging, and how to choose heavier types of mulch to prevent it washing away.
You can learn about what to do with old mulch here.
Certain plants can also help with erosion control – you can find 10 plants that prevent soil erosion in my article here.
You can learn about 7 different types of mulch for vegetable gardens here.
You might also be interested in my article on mulching raised beds or my article on mulching around trees.
I hope you found this article helpful. If so, please share it with someone who can use the information.
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~Jonathon