BRF is a common term in forestry. It is derived from the French “Bois Raméal Fragmenté”, or Ramial Chipped Wood. Anybody can make this mulch from crushed and shredded green wood branches. It’s the best mulch for enriching and protecting garden soil.
While still under the radar of the public at large, BRF/RCW is a technique known to organic gardeners the world over. Canadian scientists developed and studied the practice in the 1990s.
The basic concept is to cover the soil with a mulch of shredded and crushed young branches and sprigs freshly cut from trees. These branches, usually under 3 inches (7 cm) in diameter, act to fertilize the soil, retain water to reduce watering and eliminate the need for fertilizer and chemical treatments.
- The main difference with wood chip mulch is that ramial chipped wood requires fresh branches. That way they’re still loaded with live buds, sap, and nutrients.
- Branches should be processed within a few weeks to still retain the specific RCW / BRF advantages.
- Older, drier wood isn’t as nutrient-rich, although it still has all the advantages of wood chips.
BRF, RCW, an organic solution
Indeed, like any other mulch, BRF (or RCW in English) protects soil from erosion, evaporation and inhibits weed growth. On top of that, it retains water very well. Young branches tend to contain a great many nutrients: that’s where buds, leaves and flowers are located. These nutrients are transformed by underground fauna and flora (worms, fungus, thrips…). In the end, everything breaks down into organic building blocks that enrich, aerate the soil and balance its pH.
Result: beautiful, healthy plants and more productive fruits and vegetables.
- Note that fungus is what breaks the wood bits down into healthy nutrients.
- These fungus require nitrogen to set up shop.
- Over the first few months, nitrogen-needing plants might have a tough time, but this is more than offset after a season has passed.
Ramial Chipped Wood, a practical solution
Best spread your BRF or RCW out at the end of winter or at the beginning of spring.
- Collect branches and shoots whenever you prune shrubs and trees in your garden.
- If you don’t have enough, check with your local municipality. Often, they will let you avail of pruning waste from various landscape and gardening companies in your area.
- Crush and shred this material in a chipper shredder.
- If possible, reduce the portion of conifer branches that tend to make the soil more acidic. Keep conifers to under 20% of the content (one part conifers for at least four parts deciduous).
Spread the mulch in a layer 1 to 2 inches (2 to 5 cm) thick atop your flower beds, future vegetable beds and fruit beds.
- Studies show BRF or RCW to be effective in increasing harvests for tomato, zucchini and strawberry.
Lather it under your trees and shrubs – don’t cover the soil right around the trunk though, to keep the root crown free. Run the cultivator along the ground to stir in some of the ground bacteria. There’s no need to deep till or turn the ground. That’s all!
After that, simply sow and plant whatever you wish, as usual. Apply a new layer of BRF or RCW atop the previous one in fall of the following year. Wood chips from the first layer will already have been broken down and mingled with the soil.
Laure Hamann edited by Gaspard Lorthiois
Ramial Chipped wood, a new tool for forestry management
Considering the tree as a whole
Overall, hardwood deciduous trees make for the best Ramial Chipped Wood material. Their tips are replete with nutrients all year long:
- in spring, new growth bursts with rich sap
- in summer, tree crowns are where most of the photosynthesis occurs
- during fall and winter, buds form for the next season and contain many nutrients.
Ramial chipped wood is a great way to maximize forestry revenue. Just as a wheat farmer sets stalks aside as straw fodder for animals, tips of trees are also a potential resource.
Thinning rows of cultivated trees, a practice that maximizes growth of the most promising specimens, results in a lot of extra material. Wood is either sold or kept for firewood, but until recently, leafy fronds were simply left behind.
With ramial chipped wood mulching, this rich material can benefit fields in a completely organic and environment-friendly way.
- Note that you should still leave a portion of the materials behind. This is important for the forest soil to keep improving.
Adapting soil for new species of wood and lumber
Ramial chipped wood has the capacity to enhance and increase the quality of forest soil, too. This is due to long, woody compounds called lignins and cellulose that take up to several centuries before breaking down entirely.
- This is a form of long-lasting humus that is much richer than that derived from grassy plants and lawn trimmings.
RCW/BRF and soil pH
Plots of land where conifers have been growing for a long time tend to turn acidic. Conversely, soil that is above limestone bedrock tends to be rather alkaline.
Ramial Chipped Wood corrects these deviations and brings soil pH nearer to neutral.
- You can control soil pH with Ramial Chipped Wood.
- Actually, the resulting soil is very slightly acidic, at 6.8, which suits plants better than strictly neutral “ph 7”.
Applying RCW over a couple seasons will significantly impact the pH.
- Soil that was too acidic for higher-value wood leads to planting without fear in soil that is more neutral.
- Excessively alkaline soil reverts to a more acidic pH.
This is very relevant in tropical island countries, where most of the soil is alkaline due to pH-raising coral bedrock.
Best tree varieties for Ramial Chipped Wood
Deciduous forest varieties make for the richest RCW mulch
Deciduous trees such as birch, poplar, maple and hophornbeam are often used for RCW. They are fast-growing. When harvested at mature size, these trees can earn an extra amount from the very rich branch tips they leave behind.
Ramial Wood Chips from garden plants and trees
In a garden, many ornamental tree trimmings are suitable for recycling into RCW.
- If you need to fell a tree, prune a hedge or hatrack a runaway shrub, don’t let this precious material leave your garden!
Evergreens that aren’t conifers also make excellent ramial chipped wood, even up to 100%.
- This is good news for people growing hedges out of boxwood, cotoneaster, photinia and yaupon for instance.
- Ornamental shrubs such as Azalea, Camellia, Rhododendron also can be converted to RCW.
- You can go 100% trimmings from olive tree, citrus, and even all the waste from pruning apple & pear trees.
To avoid spreading diseases, don’t include diseased branches. If you do, don’t use the resulting mulch under the same type of tree.
- For instance, apply Bois Raméal Fragmenté from an orchard in the vegetable patch.
- BRF from forest trees can go to an orchard and vice-versa.
Non-tree sources for RCW/BRF
Don’t discriminate when clearing a lot. Simply add it all in.
- You can throw in any blackberry, ferns and other invasive plants, greens or bramble as you chip the original RCW tree branches.
- Chip them finely. If any stems are over an inch long (3 cm), they might take root and sprout like a cutting.
However, mulch made exclusively from these isn’t as nutritious as that of tree-based ramial wood chips. Since not made from tree branches, the name Ramial Chipped Wood isn’t appropriate anymore.
- Such chipped plant material is still far better than lawn trimmings however.
What not to use for BRF/RCW
A few trees (and plants) exhibit strong allelopathic properties. It’s the accurate term to say “it kills its peers”. Known examples are eucalyptus, walnut and mahogany: these exude compounds that prohibit germination and stunt growth of other plants and trees. In a way, the acidic soil under conifers is also a form of allelopathy.
As such, conifers, eucalyptus and pine trees are acceptable but only in a small proportion, under 1/10th. Indeed, they would tend to acidify soil or render it less suitable for growing compared to more “generous” deciduous tree ramial wood chips.
Smart tip about Ramial Wood Chips
Don’t really like the disorderly appearance of chipped wood and leaves? Pair RWC with other types of mulch:
Sources shared to Nature & Garden:
- Gilles Lemieux and Diane Germain, Ramial Chipped Wood, the clue to sustainable fertile soil (University of Laval in Quebec, Canada)
Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Ramial Chipped wood production by USDA Forest Service Research Operations, USDA Forest Service via Bugwood.org
RCW / BRF mulch lain down by Howard F. Schwartz, University of Colorado via Bugwood.org