What Is The Purpose Of Mulch?

If you’ve ever been to a garden center or nursery, you’ve probably seen a wide selection of mulch options in materials ranging from recycled rubber to straw and bark. But besides giving the garden a tidy look, what’s the actual purpose of applying mulch to the soil? 

Mulch is used to improve soil drainage, regulate soil temperature, and prevent soil erosion. Organic mulch can also enrich the soil with nutrients and suppress weed growth. Always apply an even layer of mulch and avoid stacking for the best results. 

Let’s take a closer look at the importance of applying mulch in your garden and what types of mulch are best. We’ll also review some tips on how to apply mulch properly so that you get the full benefit of its use.

What Is Mulch?

Black Mulch or Wood Chip Mound

Mulch is any covering used on top of the soil with the purpose of protecting the soil underneath. While most people think of mulch as only wood clippings or leaves, any organic or inorganic material that is used to cover soil can be considered mulch. If you use stones to cover the soil in winter and provide warmth to plants, it can also be considered mulch! 

It’s important not to confuse mulch with compost, even though they look similar in many cases. Mulch is used to protect the topsoil and may help prevent soil erosion, amongst other benefits. Compost is usually mixed with the topsoil and is used to enrich the soil. 

Although many gardeners are clear about the importance of compost, mulch isn’t used nearly as much as it should be, even though it’s equally important to your garden. So, what is mulch used for? 

When used in gardening, mulch helps retain soil moisture, reduce weeds, keep the soil temperature stable, and prevent soil erosion. Gardeners also use mulch to keep their garden looking tidy, as exposed soil can negatively affect the aesthetics of your garden. 

Organic Mulch vs. Synthetic Mulch

There are two broad categories of mulch: organic and inorganic (or synthetic). Both are effective at retaining soil moisture and preventing soil erosion. The primary difference between the two is that organic mulch is made from materials that decompose naturally and add nutrients to the soil. 

Synthetic mulch doesn’t decompose easily, but it can still be used to regulate soil temperature, prevent soil erosion, and suppress weeds. Both can look quite good in terms of garden aesthetics and can be used in all types of gardens, including lawn gardens, rock gardens, and landscape gardens.  

The type of garden you have usually affects your choice between organic and synthetic mulch. Lawn gardens and flower beds usually need organic mulch since the decomposing mulch will add nutrients to the soil.

Rock gardens and landscape gardens are often more suitable for synthetic mulch like pebbles or plastic and landscape fabric. 

In the end, it’s up to you to decide which type of mulch you need based on the benefits and drawbacks of each. If you want the mulch to enrich the soil’s nutrients, apply organic mulch. If you don’t want to replace the mulch often, synthetic mulch is better.

You can also apply both to your garden to get a blend of aesthetic value and soil enrichment. 

Types of Mulch 

While most people are familiar with wood chippings as mulch, there are many other types of mulch, such as pebbles, bark, leaves, grass clippings, landscape fabric, and even rubber. Let’s look at the common types of mulch used by most gardeners: 

Organic Mulch Types


Bark mulch (on Amazon) is a great insulator and is usually placed around vegetable plants and trees to protect them from frost. Bark is also easy to apply and doesn’t decompose quickly. 

Shredded Leaves 

Shredded leaves are easily available, since you can recycle your own garden leaves for the purpose. Leaves decompose much faster than wood, which is great if you want to add nutrients to your garden’s soil. 


Straw (on Amazon) is lighter than most organic mulches, but it does a great job of keeping plants insulated and preventing many diseases. It also regulates soil temperature and can also be used as compost. 

Grass Clippings 

Grass clippings are also used as mulch and are perfect for lawn gardens. They are best at preventing weeds from spreading, and they decompose quickly, making them an effective fertilizer for lawn gardens. 

Synthetic Mulch Types 

Landscape Fabric 

Landscape fabric (on Amazon) is a textile material that you can spread in your garden as a form of mulch. It’s mostly used to add to the aesthetics of the garden and doesn’t decompose quickly. However, it isn’t as effective at suppressing weeds as organic mulch. 


Gravel is great for vegetable gardens, rock gardens, and landscape gardens since it allows for good soil drainage. It also protects plants from extreme temperatures and allows useful garden insects to thrive. If you place gravel in the right areas, you’ll be able to transform the look of your garden. 

Benefits of Mulch 

Whether you’re looking to improve soil quality or protect your plants from the cold, you can use mulch to keep your garden healthy. Here are some reasons why you might want to use mulch:

To Regulate Soil Temperature 

Mulch is a natural insulator and can keep the soil at the optimal temperature, protecting plants from extreme weather. Many gardeners recommend using mulch around trees and plants during the fall to protect them from the frost. 

Dead leaves, wood chippings, stones, and other types of mulch are great insulators and will prevent the soil’s temperature from fluctuating drastically. This is helpful if you’ve planted flowers, vegetables, or other delicate plants that need protection from extreme weather. 

To Retain Soil Moisture 

Soil with mulch will retain moisture much longer than exposed soil. The mulch acts as a shield from the wind and sun, slowing down evaporation and improving the soil’s drainage. This is especially helpful in the hot summer months, where excessive evaporation means you’ll have to water the garden more often. 

If you’re using mulch for moisture retention, it’s important to choose the right type of mulch since some materials retain moisture better than others. Mulch made from wood, leaves, and other organic material is best since it won’t stop the flow of water through the soil. 

By adding mulch to your garden, you won’t have to water your plants as often, and the soil quality will slowly improve. 

To Improve the Soil’s Nutrition 

Organic mulch, such as wood chippings and leaves, will slowly decompose, enriching the soil over time. Unlike compost or fertilizer, organic mulch decomposes slowly, adding to the soil’s nutrients year-round. The only downside of this is that you have to replenish it after some time. 

By adding organic mulch to the soil, you can improve the soil’s drainage and nutrient composition, allowing worms and other beneficial insects to flourish. This will, in turn, promote faster plant growth. 

To Prevent Soil Erosion 

One of the main benefits of applying mulch is that it forms a protective layer over your garden’s topsoil. The topsoil is the layer of soil that contains the most nutrients. Rain and wind can cause erosion of this soil, leaving your garden with soil that lacks nutrients. 

Applying a layer of mulch over the soil provides a cover for the topsoil and prevents soil erosion. If you have a sloping garden or exposed flower beds, you’ll have to apply mulch to these areas since they’re more likely to be affected by soil erosion. 

To Prevent Weeds From Spreading  

One of the overlooked benefits of mulch is its use in weed control. Spreading mulch over the soil prevents weeds from getting sunlight, killing them off.

Since most weeds grow in exposed topsoil, a thick layer of mulch will make it difficult for weeds to germinate and grow, keeping your garden cleaner. While you’ll still have to remove weeds here and there, they won’t be a major problem. 

To Boost Your Garden’s Aesthetics 

One of the main reasons many gardeners use mulch is to improve the garden’s aesthetics. Black wood chips look great on a flowerbed, and small pebbles can transform a landscape garden while protecting the soil from erosion.

You can also use inorganic mulch to transform the aesthetics of your garden without affecting soil quality. 

How to Apply Mulch 

Woman gardener mulching potter thuja tree with pine tree bark mulch

Applying mulch isn’t difficult if you know how to do it properly. When applying mulch, always remember that it’s not compost, and you have to apply enough to suppress weeds and prevent soil erosion. 

When applying organic mulch, spread the mulch evenly over the target area. You don’t want to leave empty spots or apply a layer that’s too thin.

However, avoid applying too much mulch in certain areas as it could affect the soil drainage and slow down plant growth. Mulch should ideally be 2-4 inches above the soil and spread evenly. 

When applying mulch around plants, avoid stacking the mulch since it may affect the drainage and increase the risk of diseases attacking the plant. A small layer of mulch will usually last at least 6 months if applied properly, and synthetic mulch will last several years, so there’s no need to apply too much. 

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