Composting Gardening Mulching Soil

Rameal Chipped Wood (RCW) as a Mulch and Soil Amendment

by Edith Smeesters, biologist, author and speaker

A few decades ago, I was given a book by Ida and Jean Pain called “Un autre jardin ou les Méthodes Jean Pain.” The book tells the story of their garden at the Domaine des Templiers in the Var region in the south of France. Jean Pain explains how he transformed the rocky terrain into a lush garden using composted brushwood (branches from forest undergrowth): an overabundant material in his region that often caused forest fires. After shredding the brush into small fragments, he soaked it in water before composting it. The results in his vegetable garden were spectacular, even in an area where rainfall is very rare and where the temperature often exceeds 100 °F (40 °C) in the summer.

As I just about to start my first vegetable garden on what was essentially landfill, I immediately ordered a few loads of shredded branches that would otherwise have taken the path to the landfill! It was a huge success: my vegetable garden became lush and productive in less than two years.

The Science Behind RCW

Vegetable garden covered with RCW mulch.
Vegetable garden covered with RCW mulch.

At the same time, I discovered the research of Professor Gilles Lemieux, from the Faculty of Forestry at Laval University, Quebec City, Canada. It was he who coined the term “bois raméal fragmenté” or BRF—later to be translated as ramial chipped wood (RCW)—and documented its role in the “aggradation” of soils, as opposed to their degradation. Interested in recycling the huge piles of branches left behind by the forest industry, Gilles Lemieux began carrying out research on the role of the trees and especially this ramial wood in pedogenesis: the formation of fertile soils. He realized that the most fertile soils on the planet came from forests. Forest soils are self-sufficient, because their fertility is constantly regenerated by the branches and leaves that fall to the ground and are reincorporated into it thanks to the soil’s microfauna.

Mushrooms in RCW mulch
The fungi often seen in RCW mulches are part of the natural decomposition process.

The living part of a tree is located just below its bark in its cambium, that thin layer of very active plant tissue that produces both wood as it expands towards the inside of the tree and bark as it grows outward. As a result, the thinner the branch, proportionately the more cambium and nutrients it contains, nutrients that include sugars, starches, cellulose, hemicellulose, proteins, amino acids, enzymes and minerals. Freshly cut branches are preferable to dead branches. Shredding these branches promotes their contact with the soil and the RCW obtained produces a very high quality and sustainable humus thanks to the presence of lignin which will be transformed by fungi and then by the soil’s entire food chain: nematodes, insects, earthworms, arachnids, etc. RCW stimulates soil life and maintains its fertility.

The use of RCW produces remarkable improvements in the structure of all types of soils. There is better drought resistance, an increase in biodiversity, a reduced number of pests, an increase in yields, an improvement in the quality of productivity, the spontaneous appearance of mycorrhizae (beneficial fungi) and an increase in pH in the case of acidic soils. The effect of an application of RCW can be felt over 3 to 5 years.

The ramial wood harvested from conifers produces a different type of lignin than that of deciduous trees and is not as highly recommended because of it tends to inhibit plant growth. A maximum of 20% conifer wood is considered acceptable in preparing RCW.

RCW mulch used in landscaping.
RCW mulch is often used in landscaping.

In the province of Quebec, where much of the research has been done, the use of RCW is growing rapidly in horticulture and many cities now use it as a landscaping mulch. RCW is also used as a structuring material in large-scale composting operations.

Should BRF Be Composted, Incorporated into the Soil or Used as Mulch?

My European friends began by composting RCW while experiments at Laval University favored incorporating it into the soil. That gave equally amazing results, but with less work. Personally, I use it primarily as a mulch. So, which method is best?

Fungus mycelium in RCW
The mycelium of fungi links up with the roots of plants in to form a mutually beneficial symbiosis known as a mycorrhiza.

According to Gilles Lemieux, there is less carbon and nitrogen loss when incorporating RCW into the soil. It then attracts certain types of fungi that stimulate the soil’s entire food chain. Their mycelium (the hyphae of the fungi) associates with the roots of nearby plants and forms a mutually beneficial symbiotic association known as a mycorrhiza which can increase the volume of soil explored by the roots by up to 80 times, allowing the plants to absorb more minerals and water.

Is composting therefore an unnecessary and laborious step? In fact, after RCW is incorporated into the soil, the soil must still be allowed to “digest” the material for a few months. If not, it could “rob the soil of nitrogen”, causing a temporary nitrogen deficiency and you would need to provide it with nitrogen. Professor Lemieux suggests incorporating fresh RCW directly into the soil in the fall. Fungi not being hampered by cold conditions, the result is that any risk of nitrogen deficiency will be over by spring and the soil will be ready for planting.

Composting RCW first, though, means plants can take advantage of it immediately after it’s applied, but it has less of a stimulating effect on microbial activity in the soil.

RCW used as mulch in a vegetable garden
RCW used as mulch in a vegetable garden.

And then there is mulch. When RCW is applied over the surface of the soil as a mulch, it gradually decomposes on its own and does not create any nitrogen deficiency in the soil below nor in the plants. That undoubtedly explains my very positive experience RCW for the last 40 years.

Where to Find RCW?

Squash plant surrounded by ramial chipped wood.
RCW mulch gives wonderful results with both vegetables and ornamentals.

Ramial chipped wood is still often available free for the asking or else at very little expense as a byproduct of tree trimming, especially in suburban areas where many arborists are active and typically run the branches they harvest through a chipper shredder. The problem is that the shredded wood is often rather coarse, not as fine as would be ideal; plus you often have to accept delivery of a full truckload, which could be far too much for your needs! 

In all cases, do choose a contractor who maintains his shredder carefully and produces uniformly small chips. Check online for companies that work in your area or contact your municipality to see if they are harvesting branches and what they do with them. Some cities keep a supply of RCW for their own use and usually have a surplus they can share with citizens. 

Since RCW mulch helps conserve water, municipalities would do well to distribute it and encourage its use. Several companies have tried to market RCW, but it remains a living material that is difficult to pack into bags and store for sale.


Photos accompanying this post are from Edith Smeesters

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

5 comments on “Rameal Chipped Wood (RCW) as a Mulch and Soil Amendment

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  4. I use a lot of wood chips but they are not shredded like this.

    • Christine Lemieux

      Me too. I wish I could find ramial wood chips here in Nova Scotia!

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