What Is the Purpose of Mulch? (5 Reasons to Use Mulch)

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When Spring arrives, and the smell of fresh mulch is in the air, you might be wondering, what is the purpose of mulch anyway?

If you’re looking to spruce up your landscape, a fresh layer of mulch will most certainly accomplish that goal. But, mulch serves many purposes beyond looking attractive.

The main purposes of mulch are to suppress weeds, enrich the soil with nutrients, regulate soil temperature, improve moisture retention, prevent soil erosion. In essence, mulch suppresses the growth of unwanted weeds while enriching the soil allowing plants to thrive.

Suppress Weeds

Weeds are constantly on the attack, invading garden beds, spreading their roots, and taking over. Every homeowner needs a strategy to stop them or, at the very least, slow them down. One way to prevent weeds is to spray your garden beds with chemicals every year. Another more sustainable and natural way is to use mulch to suppress the growth of weeds.

Weeds need sunlight and warmth for their seeds to germinate, which is why they are at their worst in the middle of the summer when sunlight and heat are abundant. Mulch provides a thick and dense cover which blocks sunlight, regulates soil temperature, and makes the germination of weed seeds difficult. The seeds that are able to germinate likely won’t reach the surface because mulch cuts off their energy source, the sun.

Enrich the Soil with Nutrients

Organic mulch, the kind made from organic materials such as bark or wood chips, decomposes over time and adds nutrients and texture to the soil during that process. These added nutrients improve the health and fertility of the soil. Nutrient-Rich soil is ideal for plants as well as the worms and other insects that aerate the soil.

Since organic mulch decomposes, unfortunately, you have to replenish it every year.

Retain Moisture in the Soil

Another purpose of mulch is to retain moisture in the soil it covers. Mulch acts like a sponge absorbing enormous amounts of water while blocking direct sunlight, which slows down evaporation. Retaining soil moisture not only benefits plants, but it also saves you money since you don’t need to water as often.

If mulch is too dense or you pack it too tight, it can prevent water from reaching the soil and have an adverse effect. If you apply mulch yourself, make sure you understand the proper amount to apply (coming up in this article).

Some mulches retain moisture better than others. Organic mulches made from shredded materials like bark or wood are the best at retaining moisture. Other mulches, such as stones, coarse wood chips, and recycled rubber/plastic, are less effective at moisture retention because they are not as dense. These types of mulches allow water to pass through and reach the soil, but they do not absorb water, block heat, and retain moisture as well as shredded mulch.

Regulate Soil Temperature

Mulch regulates the temperature of the soil, like the way insulation works in your home. It cools the soil during hot summer days and retains heat when temperatures decrease. Drastic fluctuations in temperature are harmful to plant roots. Mulch limits the severity of fluctuations so that plants can sustain ideal growing temperatures.

Prevent Soil Erosion

Exposed soil can erode from strong winds or rainfall. Erosion can be damaging to your landscape, especially on slopes and hills. Mulch provides a heavy, dense cover that protects the soil from these elements and limits erosion.

Frequently Asked Questions About Mulch

What is Mulch?

organic mulch

When most people think of mulch, they think of the organic type that is dark brown or reddish made from shredded bark or wood chips. But, mulch is any protective ground cover laid on top of the soil. There are several different types of mulch, and each has its pros and cons. The most common types serve the core purposes outlined above (control weeds, add nutrients, reduce water evaporation, regulate soil temperature, prevent erosion), but some are simply for decorative purposes.

What are the Different Types of Mulch?

There are two classes of mulch, organic and inorganic. Organic mulch is made from natural materials such as bark, wood, compost, leaves, grass clippings, straw, and sawdust. In-organic, or synthetic, mulch is man-made. The common types of inorganic mulch are landscape fabric, plastic, rubber, stone, and gravel.

The main advantage of organic mulch is that it decomposes and, in that process, adds nutrients to the soil. The main disadvantage of organic mulch is that, because it decomposes, you have to re-apply it each year, which can be costly. It also can attract bugs and termites.

The main advantage of inorganic mulch is that, because it does not decompose, it serves as a more permanent solution and can save you money over time. On the flip side, in-organic mulch does not add any nutrients to the soil, and if you ever want to change the appearance of your landscape, you will have to remove it from your garden beds.

Inorganic mulch like landscape fabric is often used along with organic mulch. The fabric goes down first to suppress weeds, and a thin layer of organic mulch goes on top of the fabric to provide a finished look.

How Often Should I Apply Mulch?

How often you should apply mulch depends on the type of mulch you use and your climate. If you use inorganic mulch, you likely won’t have to apply more or replace it for many years. For organic mulch, landscape professionals recommend reapplying once a year in the springtime.

How Much Mulch Do I Need?

The standard metric to measure mulch is cubic yards. The amount of mulch you need depends on the size of the area you plan to cover. One bag of mulch covers two cubic yards. But how do you figure out how many cubic yards you need?

Here are the simple steps to calculate how much mulch you need:

Step 1: Measure the length and width of all areas you plan to cover in feet.

Step 2: For each area, multiply the length times width to get the total square feet. Then add up the square footage from each area to get the total square footage.

Step 3: Multiply the total square feet by the thickness in inches you plan to spread the mulch. For areas with significant weeds, your layer should be 4 to 6 inches thick. In other areas, 2 to 3 inches is enough.  If you are putting down mulch for the first time, spread it at least 3-4 inches thick. When reapplying each year, check the condition of the mulch. If it hasn’t decomposed, you only need an inch or two.

Step 4: Divide the number you get in step 3 by 324 because one cubic yard of mulch covers 324-square feet one inch deep.

Let’s make this real with an example. Say you have two garden beds, one is 10 by 10 feet, and the other is 12 by 6 feet. Your total square feet is 172 (10×10 plus 12×6). You plan to spread the mulch an average of 4 inches deep, so you multiply 172 by 4 and get 688. Then you take 688 and divide by 324, which equals 2.1. In this scenario, you need approximately 2 cubic yards of mulch.

How Much Does Mulch Cost?

If you need mulch for large portions of your yard, you should buy it in bulk. The cost of bulk deliveries can range from $15 to $65 per cubic yard. Of course, the more you buy, the lower the cost per cubic yard.

mulch in bulk

This chart shows the average prices of one cubic yard of each type of mulch, according to data from HomeAdvisor.com.

 Cost of 1 Cubic Yard
Black Hardwood$64
Dark Brown Fines$35
Double Shredded Log$24
Hardwood Oak Bark$60
Natural Fines$16
Screened Natural$24
Shredded Log$19
Pine bark/needles/strong>$5 - $6
Straw/hay$4 - $5 per bale
Wood chips/nuggets$5 - $6
Landscape cloth$20 per roll
Plastic$25 per roll
Rocks/gravel$10 per 50 pound bag
Rubber mulch$5 - $6

If you are looking to cover smaller areas, you can buy mulch by the bag at any home improvement store or online at HomeDepot.com. Inorganic mulch is available on Amazon, including Permanent Mulch Border made out of recycled rubber, Dewitt ground cover, Scotts 25-year landscape fabric, and Mexican beach pebbles for a unique look around succulents or fairy gardens.

Over time, the color of organic mulch will fade and lose its fresh look. Between applications, you can buy Mulch Colorant or Mulch Color Renewal at Amazon and stores like Home Depot to restore faded coloring and give mulch a beautiful and fresh look.

Bottom Line: Mulch Helps Plants Thrive and Limits the Growth of Weeds

To recap, the purpose of mulch goes well beyond its pleasant appearance. Mulch provides a protective cover that suppresses the growth of weeds while enriching the soil with nutrients. Its ability to retain moisture and regulate soil temperature creates an environment for plants to grow and survive even during periods of limited watering and fluctuations in temperature.

If you do it right, mulch will save you time and money in the long run. You’ll spend less time weeding and maintaining your gardens and less cash on toxic weed sprays.

What are you waiting for? It’s time to start mulching!

Do you have tips on mulching? What type of mulch do you prefer and why? Let us know in the comments below!

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3 thoughts on “What Is the Purpose of Mulch? (5 Reasons to Use Mulch)”

  1. My husband and I are planning on doing all of our own yard work for our new home, and we weren’t sure about how often we should be applying it over the years. Thank you for helping me understand that for organic mulch, which we are using, we should be reapplying once a year in the springtime. We will be sure to remember this, and hopefully, our yard stays beautiful through the years.


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