Is Mulch The Same As Compost?

By   | Last Updated :   August 4, 2021 | Filed In :   Garden Landscaping Ideas

If you’re new to gardening, you might get a bit confused when people start talking about mulching and composting.

The words mulch and compost are often used interchangeably even though it’s not technically correct. Mulching and composting is very important for gardening, but knowing the difference between them and how to use them is what sets the professional home gardener apart from your average Joe.

If you want your garden to be the talk of the town, you’ll have to know how to use mulch and compost correctly. Let’s get you started.

mulch vs compost

Mulch By Dvortygirl – Own work, CC BY-SA 3.0, (Left). Compost By ISED Solutions, via Flickr (Right)

Are mulch and compost the same thing?

Mulch and compost are not the same.

Mulch consists of either an organic or inorganic material that is used on the top layer of the soil to control weeds, erosion, soil temperature and moisture.

Compost, on the other hand, is a mix of decomposed organic materials that are worked into the soil to provide nutrients to the plants for increased growth rate, blooming and food production.

What is mulch?

Mulch can consist of organic or inorganic material such as wood chips, leaves, newspaper, bark, straw, decorative stones, shredded rubber, mulching fabrics and mulching compost that are used to cover the topsoil without being mixed in.

The process of placing mulch on the soil is called mulching. Mulch is used to retain moisture, control soil temperature, prevent weeds from growing and prevent soil erosion.

pine tree bark mulch

You can use pine tree bark to make mulch; credit: Shutterstock

Mulch can easily be confused with compost due to having some of the same qualities.

Organic mulch will also fertilise your plants as it decomposes and compost can, to some extent, be used as a mulch. Unlike compost, however, mulch can be used year-round to protect your plants from harsh climate conditions.

How to use mulch

Mulch is often used as a protective cover for sensitive plants. To use mulch in your garden, simply gather some fallen leaves or lawn clippings and spread them evenly around the base of your plants.

If you want your mulch to last a few seasons, it is best to use something more durable than leaves or lawn clippings. Cedarwood chips are a popular choice since this type of mulch breaks down slowly making it ideal for perennials. It also has a mild insect repellent quality.

You can also use other types of wood chips like pine for instance.

Mulch can also be used to protect your plants against frost and severe temperature changes.

mulch in hars conditions

Use mulch to protect plants from winter weather; credit: Pixabay

This is especially handy if you want to keep a bonsai safe during winter. Simply bury your little tree in mulch over the winter period and uncover it in spring.

If you live in an area where the soil dries out very quickly, you can use a mulch to keep it moist for longer.

What is compost?

Compost is decomposed organic material that is used to enhance the quality of your soil. It is most often mixed into the soil to benefit the plants growing there. On rare occasions, compost can be used as a mulch, but it does more good in the soil than on top.

Compost can be made at home by adding lawn clippings, kitchen scraps and other organic materials to a compost bin. Over time the materials in the bin will rot and break down into the substance we refer to as compost.

compost bin

Use a separate bin to create compost; credit: Shutterstock

If your compost is a brown colour and has a pleasant smell, it is ready to be used. This finished product is also sometimes referred to as humus.

Compost will add structure and nutrients to your soil which in turn improves plant growth, health, food production and flowering. It also has a long-lasting effect since compost will continue to decompose in your soil which slowly releases nutrients for your plants over time.

It should never be used without being mixed into normal soil since compost creates such a comfortable environment that plants refuse to send their roots outside of their compost bubble.

This can affect plant growth and production. Compost is sometimes referred to as fertilizer since it adds nutrients to the soil, but unlike fertiliser, compost won’t damage your plants when used as the primary substrate.

How to use compost

Compost works best when mixed into the soil. It will supply your plants with all the nutrients they need to grow and thrive.

compost

Credit: Pixabay

If you’re planting new plants, you can add a little bit of compost to the hole to give your plants a boost. Never fill the hole with compost since this will negatively impact growth.

If you want to add compost to the soil around your existing plants, you can either add it on top of the soil like mulch and leave it to be worked into the ground by creatures like earthworms, or you can work it into the ground yourself.

Take care not to damage the existing root system of your plants when loosening and mixing the soil with the compost.

It is best to restrict adding compost to the growing season. Your plants don’t require the extra nutrients when they are dormant during the winter months. If you’re aiming to protect your plants against the cold, rather use mulch.

Mulch vs compost – which is better?

Mulch and compost are equally important for a healthy garden. Which substance you use will, however, be determined by what you want to do.

compost and soil

Compost should always go together with soil; credit: Shutterstock

If you want to increase the growth rate, amount of blooms or the production rate of your plants, it is better to use compost.

If your goal is to protect your soil against moisture loss, erosion, weed growth and temperature changes, mulch will be your best friend.

Most gardeners use a combination of mulch and compost in their gardens since they want the benefits of both.

FAQ’s

Can I use compost as mulch?

Compost can definitely be used as mulch, but it won’t last as long. Nutrients will constantly leak into the soil and the compost will turn to mush much faster than mulch would. Mulch usually consists of undecomposed organic matter that slowly breaks down after being placed on the topsoil.

Do I need to remove mulch before adding compost to my garden?

It is best to remove old mulch before turning the soil of an annual bed. Undecomposed mulch may harm your plants. After you’ve added the properly decomposed compost and planted your new annuals, you can add new mulch on top of the soil to protect it for another year.

mulch in the garden

Add new mulch after adding compost; credit: Shutterstock

In Perrenial beds, you can simply move some of the mulch aside, work in some compost and replace the mulch. If the mulch becomes a bit thin, add another 2.5 centimetres (inch). Doing so will let you get away with only replacing your mulch every other year or when the amount exceeds 7.5 centimetres (3 inches).

Can too much compost hurt plants?

Plants can be planted in 100% compost but it’s not advised.

If your compost isn’t properly decomposed or if your plant needs to extend its roots from its little compost filled hole into normal soil, you might want to mix it with normal soil to avoid problems.

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