Last Modified: April 1, 2024

Compost Mulch


Close up of composted wood chip

By Ben Parrot - Landscape Gardener & Amateur Geologist


Wood decorative material and landscaping aggregate

Geological name(s):


Other Name(s):

Bark compost, composted bark, mulch compost, composted bark mulch, mulching compost, mulch with compost, composted mulch


Welcome to the only encyclopaedia for decorative aggregates and landscaping materials. Compost mulch, also known as mulch compost, is an economical, organic gardening product generally made from composted bark and tree by-products. It is usually produced from various types of coniferous trees, green waste products and manures for the many garden benefits, especially soil improvement. Compost bark mulch usually has a dark brown colour that creates a beautiful contrast against the plants and shrubs in your garden, highlighting their greenery and giving your beds and borders a neat and natural look. This aggregate is best suited for landscaping projects where budget and performance are important factors.

This encyclopaedia entry provides a thorough overview of compost mulch, a landscaping material and decorative aggregate. It details the type of product's general specifications, accompanied by photographs, and outlines its benefits, applications, and incompatibilities as a garden material. Additionally, this entry serves as a gateway to a wealth of DIY resources, with a list of comparable alternatives, articles offering design inspiration and fundamental principles, and a collection of straightforward, step-by-step instructions for constructing your own garden features.

Important note: As this is a general page about compost mulch, it is essential to note that variability factors exist, not just between brands but also between products from the same supplier. If a product's appearance or any other aspect is important to you, we advise requesting a sample prior to ordering.

Compost Mulch Specifications





fall safety



1mm - 10mm

white wood

Dust & Fines




diy friendly

< 5%


2 years



Green waste and bark compost


Dark to light brown


Typically fragmented and crumbly

Composting wood bark and logs

Size Range

1-10mm(< 0.2")

Fall Safety

Unsuitable for play surfaces



White Wood Content

< 5%

Dust and Fines Content


Leaf mold and home made compost on a garden bed

Fire Safety



Usually 1-2 years


Varies by supplier



Pine logs in a forest

Acidic vs. Alkaline Mulch Products

Compost mulch, a vital component for enriching garden soil, comes in various forms, each with its unique pH range, from acidic to neutral and even alkaline, influencing its suitability for different plant types and garden conditions. While neutral composts pose few issues, we cover some issues about either side of the mulching compost spectrum.

Acidic Composts

One of the two types of organic mulch, generally derived from shredded bark, green waste and wood chips. They decompose slowly and require replenishment. Pine bark mulches can acidify the soil, while some wood mulches may attract pests. Acidic compost mulches can cause a nutrient imbalance, so nitrogen-rich fertilisers, blood meal or rotted manures may be added to the product, or used for remediation.

Keeping the mulch layer 5-10cm (2-4 inches) away from plant stems helps to prevent rot and pest issues.

Alkaline Composts

Multi-purpose composts are usually professionally balanced and nutrient-rich, making them  suitable for a wide range of plants. However, many multi-purpose compost mulch products can arrive highly alkaline, particularly when bought in bulk, with the permitted upper limits of PAS 100 allowing for 8.4pH. This type is unsuitable for use with young plants, and it can alter soil pH over time and is not suitable for acid-loving plants.

An initial soil pH test is recommended to establish the pH. Future testing and blending with acidifying agents may be necessary.

Common frog on leaf mulch. Jpg


Decorative aggregates like compost mulch not only enhance the aesthetic appeal of gardens and landscaping designs but also offer functional benefits. These include improved soil fertility, enhanced moisture retention, and effective weed control. Compost mulch enriches the soil with vital nutrients, fostering a thriving environment for plants. Its organic nature supports sustainable gardening practices, making it an eco-friendly choice for conscientious gardeners. The use of compost mulch, particularly composted bark mulch or composted wood chips, adds a natural, earthy texture to garden beds, elevating the overall look of the landscape.

  • Inhibits weeds
  • Improves drainage
  • Hard-wearing
  • Eco-friendly, sustainable
  • Low-maintenance
  • Moisture retention
  • Versatile all-rounder
  • pH alkaline or acidic
  • Easy transformation
  • Non-fire safe
  • Root protection
  • Easy to lay


This section lists the types of certifications that are available for this type of product and what they are for. However, this is a guide about the generic type of product, compost mulch. There may be many brands sold under this product category, but that does not guarantee their individual compliance, and it may not always be necessary depending on individual preference.

This guide equips you with an understanding of certifications to consider, depending on their relevance to your specific use case, or whether they are deemed essential for your individual project outcomes. We add advisory for particular use cases, where we consider the certification to be critical for that type of application or situation. Any products listed on our site will always show their compliance, where it is applicable.

PAS100 standard can help to ensure that the levels of unwanted toxic elements in compost do not exceed levels deemed to be safe.





PAS100 standard

Soil Safety



Sustainable Forestry




Compost mulch are versatile products suitable for a variety of garden applications. It's particularly effective in flower beds, vegetable gardens, and around trees and shrubs, where it enriches the soil and helps retain moisture. 

In the following section, we list many common compost mulch uses in landscaping. Wherever there is a hyperlink beside an item, an article from Outdoor Aggregates about the topic is available.

Composted wood mulch around seedlings. Jpg

Inspiration and Informational Articles

DIY-Friendly How-To Guides

Need to work out how many bark chippings your project needs? Try our free bark and wood chip calculator.

Unsuitable For

The following list represents the kinds of applications that mulch compost may not be suitable for:

  1. 1
    Plantings that like highly alkaline or acidic garden soil, depending on the product's pH.
  2. 2
    Use around young plants or seedlings which need more Nitrogen, especially if turned-in to the soil.
Homegrown vegetable patch with chipped bark mulch compost

Similar Alternatives to Compost Mulch

The following is a list of decorative aggregates which are alternatives to compost mulch as a ground cover. They may offer you a more suitable variation on the primary colour, a more economical option, or a close substitute for cases where the base material may be unsuitable for the project you are creating, e.g. landscaping bark for a play area, where play chips may be safer. The price averages are based on the cost of a standard bulk bag, approximately 1㎥.








brown to red


10-60mm (0.4-2.4")



brown to red


20-60mm (0.8-2.4")



brown to red


20-60mm (0.8-2.4")





10-60mm (0.4-2.4")



white or red

5-40mm (0.2-1.6")



white or red

10-40mm (0.4-1.6")



white or red


10-40mm (0.4-1.6")





5-40mm (0.2-1.6")



Under £80







Infrequent replenishment of the mulch will be necessary to maintain the benefits and coverage.

Rake and wheelbarrow in dead leaves

Purchasing Tips

When purchasing compost mulch, consider product safety certification and future replenishments when calculating the type and quantity optimal for your project. If it is a priority, request a copy of the product's PAS100 compliance certificate before purchasing.

Our bark and wood chip calculator will give you a quick and unbiased estimate for your needs just by taking a few measurements of the space. It is one of the best and easiest ways to order the right amount and helps avoid shortfalls or over-spending. Purchasing a bulk bag of compost mulch or ordering in loose loads can offer better value than purchasing in smaller quantities. Therefore, calculating accurately can save both time and money. However, when buying in bulk, checking pH is recommended with a pH meter, prior to accepting deliveries. They are relatively cheap, especially when compared to having to remove large amounts of unsuitable compost and soil. Trust me, I have been through this before.

It is also important to consider the delivery aspects, including vehicle access to the site. Additionally, you can use our site to check stock availability and factor in VAT and transportation costs if applicable. (Feature coming soon)


What is mulch compost?

A mulch compost is a biologically active material that is derived from decomposed organic matter, or compost, and used to cover a soil surface, as a mulch. By definition, a mulch is any substance, whether organic or inorganic, that is laid to cover a soil surface. Compost is typically utilised once it has decomposed to a texture that is similar to that of soil.

What's in mulch and what does it do?

Mulch consists of decomposed organic matter such as leaves, wood, green waste and bark. It's used as a top layer in gardens to retain moisture, regulate soil temperature and suppress weeds. It helps to improve soil structure and fertility as it breaks down over time.

What are the benefits of using compost and mulch?

Using compost as mulch enriches the soil with nutrients, improves moisture retention, and supports healthy plant growth, while also being environmentally friendly. When using compost and mulch, avoid direct contact with plant stems to prevent rot, and ensure it's free from harmful pathogens and weed seeds.

How do I apply compost mulch in my garden?

Spread a layer of compost mulch around plants, ensuring it's not too thick to allow air circulation. It's best applied in late spring or early autumn. Avoid touching the stems.

Can any type of compost be used as mulch and is it suitable for all types of plants?

Most compost types can be used as mulch, but it's important to use well-decomposed, weed-free compost to avoid any harm to plants. Compost mulch is generally suitable for most plants, but some may require specific pH levels or nutrient compositions, so it's good to check for compatibility.

Is compost the same as soil?

No, compost is not the same as soil. It's a soil amendment made from decomposed organic matter, which enriches the soil when mixed in or used as a top layer.

Can I make my own composted mulch?

Yes, you can make your own compost by decomposing organic garden and kitchen waste, which can then be used as an effective mulch. Avoid adding meat and dairy products to your pile.

Where can I purchase ready-made compost mulch?

Ready-made compost mulch can be purchased through our website (coming soon), at garden centres, landscaping suppliers, or through local composting facilities.

There are many wonderful types of wood chippings available for your project needs. Check them out!

About the author 

Ben Parrot is a landscape gardener and amateur geologist. He is the founder of Outdoor Aggregates, with the mission to create the first encyclopaedia for decorative aggregates. From natural stone through to decorative bark, these aggregates are critical to garden and landscape design, universally.

The problem: There isn't any place where all the different types of decorative landscaping materials and construction aggregates can be found, nor are the specifications of each type readily available. So, enriched by his extensive experience, and inspired by the timeless elegance and raw beauty of stone and rock, etched by nature's artistry over millennia, Outdoor Aggregates was born.