Keith has been involved in the gardening and landscaping industry for the past 21 years. From a jobbing gardener to running his own landscaping services....
What is composted bark mulch?
Composted bark mulch is bark that has been composted into a dark brown, soil-like material. It is lightweight, easy to work with, and versatile. Composted bark mulch reduces soil compaction, retains moisture, and suppresses weeds. As a mulch, composted bark mulch can improve the appearance and health of your garden beds, encouraging healthy plant growth. Composted bark mulch can be used to suppress weeds and retain moisture in your garden beds.
The contents and makeup of composted bark mulch vary depending on whether you buy it commercially or make the composted bark mulch yourself.
Commercially bought bark mulch
Commercially you can buy specific tree bark mulch such as pine fines or hardwood mulches. These can contain different properties and have varying uses.
To the average gardener, the benefits of using a specific bark for mulch are debatable. Most general mulches will be more than adequate for most jobs at hand, especially if you intend to apply them to aid your plants and soil. If you were particularly looking to use them as a path you then might be concerned with the consistency of color and drainage that hardwood bark mulch could provide.
Composted bark mulch is usually available in 25 kg bags, one-tonne bulk bags, and loose bulk, depending on your Garden Center. It can be bought as plain chippings or in a composted state.
DIY made composted bark mulch
Obviously, you need bark but woodchips, twigs, and sawdust can be included too. A ready supply of these is probably easier to find than you imagine. Many arbor services will only be too happy to give you their cuttings instead of having to dispose of them. If you live near a wooded area then you will find the ingredients in abundance. It wouldn’t take very long to acquire more than enough for average size gardens or yards.
How to Compost Bark and Wood Chippings
All organic materials will decompose of their own accord. The higher the nitrogen content the quicker the decomposition process. However, bark and woodchipping have a very low carbon to nitrogen ratio so they can take an extended time to decompose. This is not necessarily an issue if you have plenty of space and time but otherwise, you have a couple of options.
- As the material will break down naturally you can use it as a mulch around plants and shrubs;
- you could add it to your existing composting pile and use the compost as you mulch;
- you could add an activator to the bark and wood chips pile and turn it regularly which will speed up the decomposition process
- If you have the space just leave it in a pile and turn it regularly, the bark and woodchips will break down naturally and will be ready for use in nine months to a year.
How to use composted bark mulch?
It is easy to apply, just spread the composted bark mulch evenly over the area. Composted bark mulch can also be used to improve the soil. This is achieved by digging the mulch into the soil to a depth of approximately 30 cm.
As a soil additive, composted bark mulch can improve soil structure, increase its water holding capacity, improve nutrient availability, suppress weeds, and increase soil aeration.
Mulch may be put down at any time of year, but the optimal time is mid-spring when the soil has softened. It is possible though that plant development may be hindered if the fertilizer is administered too early in the season.
Over generally clean and weed-free soils, mulch should be placed two to three inches thick. If you are concerned about weeds you can mitigate the chance of weeds from growing by using weed cloth, newspaper, or cardboard before you apply mulch.
Before adding mulch, make sure the soil is well hydrated this helps decomposition which in turn will feed and enrich the topsoil.
Best places to use composted bark mulch
Composted bark mulch can be used for path construction. The mulch can be laid directly on the path or mixed with compost to create a path base. The mulch retains moisture, creating a softer path. In addition, it can be used around sheds, paving, and driveways helping drainage.
Lawns and garden beds
Composted bark mulch can be used for top-dressing lawns to create a neat, well-groomed appearance. It can also be used to fill hollows and create sunken garden beds.
Putting down a layer of bark mulch on your lawn can also be a great way to protect your lawn from winter weather. It will insulate the lawn, keeping the soil temperature more consistent, and allowing it to retain enough moisture in the soil for it to remain healthy but protect it from frost.
Applied around shrubs and trees
Composted bark mulch can be used around shrubs and trees. It can help retain moisture, prevent weeds, improve soil structure and increase plant health. Composted bark mulch can be used around vegetable beds to suppress weeds, retain moisture and improve soil structure.
There is some debate with regard to using wood chips and tree bark as mulch around plants. The argument is that the wood and bark have a very low carbon-to-nitrogen ratio (C/N) meaning that they leach nitrogen from the soil as they break down. The extent and the effect of this is hotly contested.
Jeff Gillman argues that “the truth is that some nitrogen from the top layer of soil is used up when woodchips are initially broken down by bacteria but this nitrogen loss is likely to affect only the most tender annuals, and even they probably will not sustain any permanent injury!” adding that “the idea that extra nitrogen fertilizer is needed when using woodchip mulch is just wrong.”
Linda Chalker-Scott argues “that a zone of nitrogen deficiency exists at the mulch/soil interface, inhibiting weed seed germination while having no influence upon established plant roots below the soil surface. For this reason, it is inadvisable to use high C:N mulches in annual beds or vegetable gardens where the plants of interest do not have deep, extensive root systems.” 
Unless what you are planting has a shallow root structure then this shouldn’t be an issue. In fact, as the bark and woodchips become compost, they actually provide nutrients back into the soil. So while there might be some shallow leaching of nitrogen in the initial stages this is returned as the organic material becomes finished compost.
Common Questions Asked
What is the difference between mulch and bark compost?
Any organic material that is applied to your plant beds as a top dressing or as a protective cover is referred to as mulch. It is possible to use many types of mulches as a top dressing such as compost mulch or bark mulch or sawdust or to shred leaves or pine needles.
Why would you use mulches are used by landscapers for a variety of reasons:
Mulches are used by landscapers for a variety of reasons in the garden. Mulch prevents weeds from developing, retains moisture in the soil, and regulates soil temperature throughout the growing season. Perennials, roses, and other delicate plants can be all well-protected by mulch in the winter.
Mulches provide texture and color to garden beds, making them more appealing to the eye.
Tree bark is shredded into various grades from fine to large and used as a mulch for your flowerbeds.
Can you use compost as mulch?
Yes, you can use compost as mulch. Indeed all organic mulches eventually decompose into compost. In fact, compost mulch has all the advantages of traditional, non-organic mulches, with the extra benefit of nutrition leaching into the soil. Both nitrogen and carbon from the compost seep down into the soil when water passes through the compost layer.
When using mulch, a thicker layer of mulch is preferable to a thinner one in order to protect the plants from sunlight. All of your perennials should have a three to four-inch covering of compost applied to the soil surrounding them, extending about ten to twelve inches around each plant. During the growth season, as the compost slowly seeps into the soil below, you’ll want to keep adding new layers every few months.
 Jeff Gillman: Decoding Gardening Advice
 Dr Linda Chalker-Scott: Wood chip mulch: Landscape boon or bane?