Does Mulch Helps With Drainage? Not the Whole Story

How much do you know about mulch? Did you know that mulch is used for more than just an aesthetically pleasing cover on top of the soil? Mulch can help with your garden’s drainage issues and so much more; it can make or break a garden. 

Mulch helps with drainage in a garden in the following ways:

  • Helps with retaining moisture in the soil and prevent evaporation
  • Improves soil structure to prevent pooling
  • Helps with soil compaction and erosion
  • Helps to capture runoff water, increasing the absorption rate
  • Prevents precipitation damage

Mulch plays an integral part in most gardens today, as it helps with drainage issues and so much more. Mulch can also help with plant establishment, preventing disease, seed germination, reducing pesticide use, and accelerating soil desalinization.

Does Mulch Help With Drainage?

Mulch does help with drainage. Many a gardener and landscapers alike love to work with mulch, as it brings many positive elements to a garden. Getting your garden beds to look pretty when using mulch is a bonus, as mulch is most importantly a vital part of landscape management.

Mulch is commonly used to:

  • Retain moisture in the soil
  • Improve the soil’s structure to prevent pooling (organic)
  • Improve drainage 
  • Help prevent soil erosion
  • Keep the soil cool
  • Prevent frost heaving in winter
  • Prevent precipitation damage
  • Suppress weed growth
  • Provide nutrients to the plants and trees as they decompose (organic)
  • Increase the root temperature of plants

Mulch Helps With Water Pooling

Most gardeners or landscapers have had to deal with the problem of pooling/ponding in their lives. Ponding occurs when an area in your garden can’t drain water away, ending up covered in mud or a pool of standing water.

Clay or compacted soils is typically the culprit when it comes to pooling and can be corrected by the following methods:

How To Use Mulch To Combat Pooling

Let us look at how mulch can help with regards to pooling in your garden by following these easy steps:

Step 1

Identify the garden area with the pooling problem by laying a garden hose around the perimeter,

Step 2

Choose the best mulch that will fit into this area, either organic or inorganic mulch. Organic mulch includes materials such as:

  • Wood Chips
  • Compost
  • Leaves
  • Straw
  • Manure
  • Grass Shavings

Inorganic mulch includes:

  • Recycled Rubber
  • Decomposed Granite
  • Gravel
  • Processed Glass

Be advised that organic mulch will break down over time and should be replaced yearly. Blending it in the soil will increase the soil’s overall quality. Inorganic mulch will last much longer but know that it can affect future use of the area used in.

Step 3

Fill the pooling area with the mulch and create a layer that the water can drain through so a visible pool is no longer visible. Using this method will instantly improve your garden; however, underlying issues with a too dense soil type or an improper slope will remain. 

Digging a trench through the area, filling it with inorganic mulch such as gravel can promote drainage.

Step 4

Use a rototiller or shovel to work organic mulch into the soil- digging to a depth of 8-inches minimum- getting below the compacted layer. Test the soil’s workability by squeezing a handful of soil:

  • If the soil crumbles apart, it is ready.
  • If the soil forms a ball, it’s still too wet.

The soil drains better when it contains organic material like:

  • Manure
  • Compost
  • Mulch

Mixing mulch into the soil can help to change it in a way that can prevent or minimize pooling.

Step 5

When you are finished mixing the mulch into the soil’s top layer and spreading it on top of the soil, rake the mulch so that it slopes away from the pooling area. Be careful not to direct the runoff towards your house, for then you will be sitting with another problem. 

The mulch will raise the level of the affected area, adding volume, ultimately improving how the soil drains, and will keep water from pooling.

If you are looking for other methods of draining and wondering which is best for you, read here to see what other options you have.

Mulch Helps With Moisture Retention

Mulch will improve soil moisture. When soil is bare, it is exposed to heat, wind, and compaction, losing water through:

  • Evaporation
  • Inability to absorb rainfall and irrigation

Using mulches will result in the soil having greater water retention and reduced evaporation. When applying straw mulch, you can expect to see a reduction of evaporation of up to 30%. Organic mulches conserve any water source with more significant effects and also do not limit:

  • Soil water infiltration
  • Soil water retention

Organic mulch helps to protect soil water reserves by holding water until saturated for later release and prevents runoff where the soil gets almost no benefit from the water. Mulch also does an excellent job of protecting trees, shrubs, and plants from drought stress.

Moisture-loving plants love mulch, plants preferring dry soils not so much and maybe hindered by the moist nature of mulch protected soil.

This is also the reason that if your bed it next to your house you may want to create a barrier of non-organic material. There are many other complexities to consider a bed next to your home, so we created a guide to help you through it.

Mulch Helps With Soil Compaction And Erosion

Applying mulch protects soils from wind water, erosion, and compaction that directly impacts seeding, tree growth, root stress, which causes general poor plant health. Compacted soils increase surface runoff and erosion because of reduced water movement into/through the soil.

Soil erosion happens when surface runoff water becomes heavy and rapid enough to carry away soil particles. The altered structure and reduced drainage capacity of compacted soils often result in runoff or standing water.

It’s easy to identify compacted soils on your property. You will notice that these soils are difficult to dig up with a shovel, especially when the soil area is dry. Individual clods tend to be large and difficult to break apart.

Even if you decide to add a thin organic mulch, the soil protection will start. Using one of the following mulch types will help reduce erosion and overland water flow:

  • Pine needles
  • Wood chips
  • Straw

To restore compacted urban soils aggregation and porosity, use the following mulch on it:

 Being proactive when it comes to mulching will protect the integrity of the soil. Prevention is better than curing compacted soil. Applying mulch before compaction occurs is seen as a brilliant gardening maintenance plan.

Mulch Helps With Optimal Soil Temperatures

Mulch has proven to lower soil temperatures during hot summer months, which tend to play a very prominent part in killing fine plant roots, causing stress and root rot. Whether temperatures are extremely hot or extremely cold, mulches protect soils from them. 

Coarse mulches (pine chunks) moderate temperature better – allows for better gas and water transfer – than thick layers of finely textured/ double shredded mulches. 

A layer of mulch can do wonders in keeping soils from getting too hot, which is very helpful when trying to grow sensitive plants in hot climates. When soils overheat, they can be rendered sterile and kill helpful organisms. Ensure you do proper research regarding the best mulch types for your climate.

In colder climates, a decent layer of mulch can help protect against daily frost and the thaw cycles that go with it, protecting perennials. Some inorganic mulches, like light-colored crushed stone/gravel and exposed plastic, may overheat the soil. 

Some mulches can heat soil as a function of solar radiation absorption, more than bare soils ever could.

Mulch Helps With Reduction Of Salt And Pesticide Contamination

In arid landscapes, evaporating water often leaves behind a crust of salt. Reduced evaporation due to mulch ensures that water is left in the soil and dilutes the salts. Organic mulches can actively:

  • Accelerate soil desalinization
  • Help to degrade pesticides and other contaminants

Inorganic mulches can’t bind ions and are not effective in this regard.

Mulch Helps To Improve Plant Establishment And Growth

Mulches are known to do many wonderful things when applied in the garden and aid the establishment of many herbaceous and woody species. The improvement in water retention when using mulch allows roots to establish and extend farther from the tree or plant’s trunk than when growing in bare soils.

Organic mulch improves:

  • Seed germination
  • Seed survival 
  • Enhances root establishment
  • Transplant survival
  • Plant performance
  • Plant stability

Root development will be more significant under organic mulches when compared to plastic or bare soil. Film and sheet mulches encourage root growth on top of the specific mulch but tend to injure the plants when it needs to be removed. 

Plastic mulches typically lead to:

  • Increased mortality of transplanted plant material
  • Damage to delicate root systems

Plant roots tend to grow into organic mulch layers, and this mingling of matter doesn’t appear to injure the plant or its root systems.

Mulch Helps With Reduction Of Disease

You have to love mulch. Mulches will actively reduce the splashing of irrigation and rainwater, which tend to carry disease spores to the stems and leaves of plants. Whole populations of beneficial microbes that can reduce soil pathogens can be increased with organic mulches.

Like a security unit, mulches will combat disease organisms directly as well. On the other hand, some plastic mulches can increase the incidence of disease when exacerbating already poor soil conditions that can lead to various types of rot.

If you are wondering the type of disease your plant has than check out this quick resource to help you narrow it down.

Mulch Helps With Weed Reduction

Mulch is a gift that keeps on giving. This time, it’s the gift of controlling weeds in your garden. Mulch can reduce the seed germination of many a weed species, reducing the light exposure needed to germinate. It also stresses existing weeds and stops new weed growth in its unwelcome tracks.

Coarse mulch materials are more effective than finely textured mulches. The act of reducing weed growth results in more water for your plants and trees. A layer of mulch – at least 1″ deep (aim for 3″ in most scenarios) will generally help with suppressing weeds. 

Some organic mulches may spread some unwanted seeds that can grow within the mulch like:

  • Compost that has not experienced proper heat decomposition
  • Hay that contains seeds from plants growing in the field

Mulch Helps To Reduce Pesticide Use

When you mulch your garden, you reduce weeds, plant stress, and susceptibility to pathogens and pests, which results in reduced use of:

  • Insecticides
  • Herbicides
  • Fungicides

Organic vs. Inorganic Mulches

Organic mulches are very good at absorbing water; these mulches include:

  • Bark
  • Wood
  • Leaves
  • Compost
  • Hay
  • Straw
  • Greenwaste
  • Grass clippings
  • Manure

Organic mulch acts as a giant sponge by absorbing and holding on to excess water, slowly releasing it into the air and soil. These mulch types will reduce the need for water, helping you to conserve water and prevent polluted runoff from flowing into the local waterways and ocean.

This is not to be confused with any sponginess in the ground surrounding your bed as that may be caused by something else entirely, read about it here.

Inorganic mulches do not absorb water and can include:

  • Gravel
  • Plastic
  • Rubber
  • Geotextile mats
  • Landscape fabrics

Some of these inorganic mulches like rock, stone, and gravel can provide the following benefits:

  • Air and water movement
  • Preventing loss of soil moisture by reducing evaporation
  • Weed control

For example, synthetic mulches (black plastic) are not used to absorb water and may inhibit water reaching the soil. Choosing organic mulch over the inorganic mulch types to assist with drainage issues is usually the best choice.


Mulch that is applied correctly will enhance your garden’s drainage positively. Whether you are struggling with compact or clay soil, mulch can effectively change how your soil behaves and improve its drainage capabilities.

Problems with water runoff, erosion, soil moisture, moisture and water evaporation, and pooling can all be addressed by using the correct mulch. 

Manny Moore

Getting my hands dirty and building a place that me and my small family love is a driving factor for what I do and how I do it. I want to share what I have learned and practiced so that it is just that much easier for everyone to have another tool in their tool belt. Your home should be a place that you love and feel comfortable in and your backyard should be no different.

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