Does Mulch Decompose?

If you’re someone who enjoys the process of growing and maintaining a beautiful yard or garden, chances are you’re familiar with mulch and all the benefits it brings. Maybe you’ve already gone through the process of selecting and spreading your chosen mulch and are now wondering what comes next.

If you’re curious about all the details of what exactly happens with your mulch after it’s spread, this article will go over everything you need to know.

What Exactly Is Mulch?

In order to better understand everything that mulch does, it’s helpful to know exactly what it is. Mulch is a material that gets spread over the soil’s surface, often made of bark, pine needles, or leaves.

It helps to retain the soil’s moisture, keep the soil cool, and to suppress weeds. They can also help improve the soil’s structure and nutrient levels, as well as make garden beds look more attractive.

There are two different forms of mulch—organic and inorganic. In the organic category are things like leaves and bark, as well as straw and grass clippings. These forms of mulch decompose and will need to be replaced, but in the process, they will improve your soil’s structure and organic content.

Full of nutrients that your garden and yard find necessary, organic mulch is incredibly beneficial if you want lush, healthy plants.

Next is inorganic mulch, which does a great job at blocking weeds and holding in moisture. This consists of synthetic materials like black plastic, landscape fabric, and stones, and gravel.

These don’t add any nutrients to your soil, but are great at their function and don’t decompose like organic mulch does. Many people like to add a thin layer of bark mulch over the plastic or fabric, which helps to cover it up and give it a more natural look.

How Long Does it Take for Mulch to Decompose?

  1. Bark

Best used around trees, shrubs, or places you won’t be doing a lot of digging, bark mulch is a popular and long-lasting option. If left undisturbed and maintained properly, it can last from 7-10 years. For longevity, it helps if the bark mulch has constant contact with the soil underneath and receives water regularly. This helps the bark to shed in a relatively healthy way and to slow down degradation.

2. Grass Clippings

Grass clippings are best suited for more remote areas of your yard or garden since they have a high water content and therefore decompose very quickly, which can bring a somewhat unpleasant odour. It’s best to use a mulching mower with grass clippings to ensure that they get distributed properly, as there is a risk of them being spread too thick and suffocating the grass below.

3. Shredded Leaves

Shredded leaves are a very versatile option that comes with the bonus of being free. They can be used almost everywhere, although a popular choice is using them in vegetable gardens since they’ll bring more earthworms.

Shredded leaf mulches tend to break down fairly quickly and blend into the soil, so that’s something to keep in mind if you’re worried about this mulch option being somewhat unsightly. When using leaf mulch, it’s a good idea to make sure the leaves are shredded, as unshredded leaves may end up matting together and repelling rain.

4. Straw and Hay

Mostly popular in vegetable gardens, straw and salt hay are a somewhat long-lasting, nice-looking option to use as mulch. They decompose quite slowly, lasting the entire growing season all while keeping soil-borne diseases from reaching the lower plant leaves. Straw and hay mulch also makes for a nice home for beneficial insects like spiders, who will assist in keeping the pest population under control.

5. Plastic and Landscape Fabric

Moving on to inorganic mulches, plastic, and landscape fabric makes for a good choice around foundation plantings such as shrubs and trees. Since you won’t be working in and around these beds regularly, you don’t want to have to worry about going in and weeding throughout the summer, which the layer of plastic or fabric will prevent entirely.

The plastic gets very hot in the summer, killing off any weed seeds before they even get the chance to grow. Unfortunately, this means that it’ll also kill many good things in the soil, such as microbes and plant roots. In order to prevent this, make sure there is sufficient moisture by cutting holes in the fabric to allow water to pass through.

Plastic and landscape fabric are inorganic materials, meaning they won’t decompose the way organic mulches do. While they’ll last a long time in your garden, they’ll also eventually start to break down and will stop doing their job as well, so they will need to be replaced at some point.

6. Stone and Gravel

Stone and gravel work wonderfully as mulches in areas that like a little extra heat or require good drainage. They can also provide a very appealing look and can help cater to a certain aesthetic, and last an incredibly long time.

This is great if you want something you can just set and forget, although if somewhere down the line you want to change out your mulch, it will require some effort to remove all the stone. However, that may be very much worth it for this good-looking, low-maintenance mulch.


Mulching your yard or garden brings many great benefits, although deciding which mulch to use requires a fair bit of research and planning.

Organic mulches all decompose over varying time spans, which is an okay trade-off considering all the nutrients they add to your soil. Inorganic mulches take much longer to break down and are often lower maintenance, but they don’t add much in terms of nutrients to your garden or yard.

When deciding which mulch to go with, it’s a great idea to consider the decomposition time—something that will happen to all organic mulches.

If you want something that doesn’t break down quite so fast, going the inorganic route might be for you. Either way, there are many great benefits to mulching your garden, and with all the different mulches out there, there’s an option for everyone!

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