Using Crushed Concrete as Mulch (The Pros and Cons Explained)


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Using concrete as mulch can benefit plants whether they are landscaped or planted in a pot. Concrete with its white hue can also bring a modern look to plants while at the same time increasing property value.

When used as mulch, crushed concrete can prevent soil erosion, loss of moisture, and unwanted weeds from growing around plants. Concrete should be applied 2″ from the base of the plant at a depth of 1 – 2 inches. It should not be packed down as they will settle naturally over time.

Crushed concrete mulch can be easily obtained as a recycled product from an old project or a recent home renovation and can be utilized for walkways and driveways. 

In this article, we will explain the pros and cons of using concrete as mulch and what you can expect if you decide to do so.

When mulching you can use this mulch barrier that we use from amazon which is durable and gives a clean finish. You can find it by clicking here.

The Benefits of Using Crushed Concrete as Mulch

Concrete Mulch maintains soil moisture, represses weeds, and gives a finished look to planting beds, and as it is fireproof, it is used around the buildings as a band.

Cost

The cost of using crushed concrete as mulch is little to none if you are recycling it from an old renovation. However, the pieces of concrete should be uniform or close to uniform in size before it is applied as a mulch.

Moisture Retention

It can help gardeners by reducing the frequency of plant irrigation.

The loss of moisture from the soil is one of the abiotic factors that lead to dry arid soil. The soil in this state can become hydrophobic and repel water causing areas where the water sits on top of the soil for some time before it becomes fully absorbed into the soil. 

Limits Weed Growth

Concrete Mulches can potentially reduce weed infestation, evaporation and enhance the percolation and retention rate of the soil. Additionally, weeds will not only take moisture but also nutrients away from the soil making it harder for surrounding plants to thrive.

Does not Wash Away

It doesn’t wash away in a downpour or any unfavorable climatic condition, and it gives a beautiful look to the areas where it is used. This is because of the white hue attributed to the silica of which the concrete constituents are made and the weight of the concrete material.

The material used in mulching works as a protector of soil from wind and water erosion.

Maintains Soil Temperature

In addition to this, concrete mulch also maintains the temperature of soil by covering the soil’s surface, which is very necessary for the better growth of crops. 

The whiteness of the concrete apart from providing shade to the soil beneath reflects sunlight away from the soil and prevents water evaporation, keeping the soil moist longer.

In colder seasons, the concrete will also insulate the soil from the external cold preventing frost on roots and sustaining plant growth.

Disadvantages of Using Crushed Concrete as Mulch:

Soil compaction (because of weight):

Soil compaction is when stress is applied to a soil causes densification as air is displaced from the pores between the soil grains.

Concrete mulch is dense and has enough weight, which applies stress on the soil, and that suppressed soil is unable to absorb rainfall, leading to runoff and erosion.

As the spaces between the soil are vital for root growth. Concrete much which presses the mineral grains together leaves little room for water and air, leading to the difficulty for development of the roots.

Besides this, burrowing animals also find it a hostile environment because the denser soil is more difficult to penetrate. 

Weeds

In comparison to organic mulches, crushed concrete mulch organic will prevent weed only to an extent. This is because there will be greater spaces between the pieces of concrete than if an organic wood mulch was used.

An easy way to fix this is ti mix smaller wood chips with the concrete mulch so that it fills the gap between the spaces.

When Using Landscaping Fabric

Landscaping fabric is a good way to prevent the concrete mulch from being mixed into the soil which will be a pain to remove afterward. Using landscaping fabric before mulching also gets buried into the soil from the weight of the concrete over time as it settles.

This removal can be tricky but we have done this before and there is an easy procedure for the removal of landscaping fabric which we have written in our detailed post.

Unwanted Debris

It traps leaves and other debris compared to organic mulches as it is easy to remove that from the organic mulches. The debris will break down over time forming fertile soil for weeds and other unwanted plants to grow. 

Then the removal of these weeds can be difficult as it will have to be done by hand.

Removal

The removal of concrete mulch is also a complicated process as it becomes challenging over time. This is because of its weight and it sinks into the soil if no underlying fabric is used.

Lack of Potential Nutrient

Like most inorganic mulch, concrete mulch does not feed soil because it can’t provide nutrients. 

Organic mulch will break down over time. They can be easily be incorporated into the soil which can help increase the organic material in the soil and boost plant growth by feeding microbes in the soil. 

Crushed concrete mulch will not add any such benefit to the soil.

What Plants or Where can You use Concrete as Mulch:

Crushed concrete mulch is generally used around trees that have been already established with a thick or strong trunk structure.

It is often used around the trees such as:

  • Shrubs
  • Drought-resistant sub-shrubs, such as Sage or Lavender. 
  • Lilly bed Citrus trees.
  • Cherry tree.
  • Dogwood.
  • Ginkgo.
  • Hickory.
  • Hornbeam.

They are also used around the buildings:

  • The heat is radiated back out after the sunsets, helping to regulate the heat of the property.
  • It’s material used for landscape driveways, walking paths, and flower beds.

Mulch Depth When Using Concrete as Mulch: 

The depth of the mulch is dependent on the mulching substrate, and for various sizes of concrete mulch, the depth is as follows: 

  • 1-1/2” in size should be 1 – 2” deep.
  • 1-1/2” to 2” will need to be 3” deep.
  • 2” to 4” concrete can just be placed on top of the soil.

Keep in mind that this is to provide total coverage so that the landscape fabric cannot be seen through the gaps in the crushed concrete. 

The total square footage must be calculated which is then divided by the required size to calculate the total cubic yards of material you may need.

Do you Need a Mulch Barrier with Concrete Mulch

You don’t need a mulch barrier with crushed concrete mulch. It generally doesn’t need a mulch barrier because of its weight. Concrete by itself is a heavy product and is difficult to wash away when it rains or when water is run through it. This is common with wood and other types of lighter mulch.

Using a barrier with concrete will not add that retention factor. It will instead help beautify the area that the concrete mulch is being used.

It forms a seamless barrier that will distinguish grass and other shrubs situated close to or around the mulched area. 

Will Concrete Mulch Harm Plants

Plants can be affected by cement and concrete because the limestone (calcium carbonate) it contains can directly affect the pH of soil, increasing its pH to high alkaline levels. This increase in pH reduces the solubility of the minerals in the soil making it less available for plants to absorb.

When using crushed concrete, ensure that it is washed so the dust remains are no longer present. The dust can easily move into the soil by rains which will affect the pH of the soil.

When the dust is washed off, the crushed concrete is already in a cured and stable state so it will not leach any further calcium carbonate into the soil.

Apart from this, soil compaction is also a concern (mentioned above) where the soil is compressed which rescues pore spaces and can stifle root growth preventing the development of plants.

The Takeaway

Using Concrete as mulch can enhance nutrient accumulation in the soil by preventing soil erosion, and regulating temperature. Concrete suppresses weeds and enhances moisture in plants while at the same time beautifying the garden.

Intrinsically, Concrete is dense, and it has a negative impact on soil underneath. 

Its high density compresses the soil, leading to less porosity, thus degrading the soil’s air absorption capacity. 

Along with this, the depth of concrete should be kept in mind while making the concrete mulch.

In a nutshell, using concrete as mulch is advantageous for plants, soil, and scenic attractiveness that can be used around more larger and established plants or trees.

JayLea

JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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