Designing Landscapes: Fungal soil — what is it and why do we want it?
In a previous post, An Orchard In the Front Yard, I mentioned how wood chips make a good mulch for woody plants. To go a step further, you want to use ramial wood chips, which are wood chips made from the outer reaches of a deciduous tree. That means the smaller branches, including the leaves if possible, and not so much the trunk and thicker branches (the rule of thumb is nothing more than 2.5 inches thick).
Why do we want ramial wood chips?
It’s because we want a fungal dominant soil. We want a soil that’s full of the beneficial fungi that help woody plants grow vibrantly and resiliently.
The term ramial is based on a french word, rameal, which means ‘related to the small branch’. It was coined by the French Canadian, Prof. Gilles Lemieux, who pioneered the research.
The ideal soil for woody plants contains beneficial fungi and these “fun guys” thrive with the addition of ramial wood chip mulches. This type of mulch has the optimum balance of carbon to nitrogen and higher nutrient content than other wood chips. This optimum balance is due in large part to the greater ratio of cambium and recently living cells vs. old dead wood cells. It makes sense that using wood chips made with more live tissue or recently-living tissue will have more nutrient value than chips made from older wood, which is mostly carbon.
It’s like if we were to eat an animal, we’d want to eat the meaty areas and organs for the nutrients. We don’t want to eat hair, bones, and cartilage.
So for feeding fungi, the ideal wood chips should be obtained from freshly cut smaller branches with the leaves still on them. That’s where the most nutrients reside and the good fungi love that.
What do the fungi do?
Beneficial fungi are certain species of fungi that protect our plants from disease by:
- Out-competing disease organisms
- Creating a healthy soil biology
- Offering direct protection to our plants by producing anti-pathogens
- Providing nutrients and water directly to the plants for better plant health
Quick quiz: Does anyone remember where the antibiotic ‘Penicillin’ came from?
Answer: It’s a compound originally produced by certain Fun Guys to ward off the Bad Guys!
One type of fungi, called mycorrhizal fungi, physically attaches to the roots of woody plants and extends the “reach” of the plant’s roots, mining for water and nutrients in the soil that plants alone have a hard time accessing with their own roots.
The body of fungi, called mycelium, consists of strands that form massive ‘string networks’ within the soil and have tremendous surface area contact with the soil. This fungi network is more efficient at gathering water and nutrients than a plant’s roots are.
The fungi feed the woody plants with the nutrients and water that it has extracted from the soil, and the woody plants feed the fungi food sugars it has produced via photosynthesis which the fungi cannot produce itself. Fungi do not photosynthesize, this is one of the major characteristics that distinguish fungi from plants.
The connection between the fungi and the plant’s roots is intracellular. There is chemical communication going on along with the nutrient exchange. The relationship is symbiotic and has evolved over thousands of years. It has been shown that it goes further than one fungus and one plant; that the fungi connect nearby plants to each other as well. The chemical communication goes on between multiple plants via the fungus.
The forest is One
In forests, it has also been shown that when trees die, they channel their remaining nutrients out into the fungi web to feed other trees. Or a sick tree may receive nutrients from healthier trees. The term “mother tree” has been applied to the largest trees in a forest as these matriarchs actually preside over the health and well being of all the surrounding trees.
The forest is One.
Okay, that might be an exaggeration perpetrated for dramatic reasons, but many trees are connected together and it’s hard to tell how far it extends. So, in an old growth forest, perhaps it is possible. Point is, at the very least, it is a network. Who knew the very first Internet was invented by a fungus.
It’s interesting that we did not discover this fact until very recently. We divided the plants into the Plant Kingdom and the fungi into the Fungal Kingdom and assumed these two abided by our abstract separation; rival factions following the ‘laws of the jungle’, doomed to compete for the same resources ’til the end of time, an adversarial relationship.
We were wrong.
You could say we couldn’t see the forest for the trees. We were reductionist instead of holistic. It seems to be a common human flaw.
Luckily, we know better now. Now it is our duty to restore and encourage these systems, for greater ecosystem health and benefit. That includes us.
An interesting parallel in human health
We are now discovering that our own health depends on the health of the microbes in our gut. Just like mycorrhizal fungi have a symbiotic relationship with plants; helping the plants by increasing nutrient uptake and offering disease protection in exchange for food; the bacteria in our gut, in a similar role, offer our bodies nutrients and protection in exchange for comfortable living quarters within us (all the meals you can eat and a cozy 98 degrees all the time!)
By conservative estimate, in a healthy human, there are more beneficial bacterial cells in our body than there are human cells in our body. It is also evidenced that if we lose or kill off these beneficial organisms in our gut, we can become sick very quickly, even exposing us to the possibility of death.
This reframes everything. A classic paradigm shift. We can now think outside the box that we made for ourselves and put ourselves in.
We as individual humans are not an organism. We are We. We are a super-organism.
Who are we really! More ‘germ’ than human?
Back to the wood chips…
What about coniferous wood chips?
When sourcing wood chips, not only is ramial chips what you’re looking for but it’s also preferable to avoid coniferous wood chips as they tend to have naturally produced compounds that inhibit beneficial fungal growth. Coniferous wood chips actually feed a different sort of fungi that produces allelopathic compounds that inhibit beneficial fungi and decay.
However, coniferous wood chips are still better than bare soil. Keep that in mind if that is all you have available. In that case, if you think your plants are being stunted by the coniferous wood chips, I’d think about top-dressing the wood chips with compost or manure to help overcome the anti-good-fungus properties of conifer wood chips. Both compost and manure bring a litany of microbial ‘helpers’ to assist with the breakdown of the unwanted compounds as well as providing nutrients directly to plants.
So, how can you tell you have a fungal soil?
One way, the crude method, is to dig into your mulch/soil interface and see if it’s populated by white strands. These are the hyphae strands, the mycelium, or ‘body’ of the fungi. Although, I wouldn’t recommend digging stuff up if you don’t have to. It disturbs and kills the fungi to expose it and breaks its hyphae connections. Don’t worry though, if the conditions are right and the soil is well populated, it will undoubtedly recover.
A less intrusive method is to simply watch after the first soaking rain following a warm dry spell. If the soil is colonized with fungi you can expect mushrooms to sprout everywhere. It’s a wonderful sight to see and an indicator of healthy, fungal dominant soil.
What about mushrooms coming out of the stems or trunk of your plant?
Mushrooms coming up out of the ground are a good sign. On the other hand, mushrooms sprouting from the trunk of a tree or from the stems of your plant is a bad sign indicating rot is pretty extensive within the plant. It’s not necessarily the fungus that has caused the plant to be infected, but it is a visual indicator that rot is extensive enough that the fungus has reached a point where it feels “comfortable” enough to start reproducing. At this point, the prognosis is not good for your plant, or at least the section of plant that is infected.
This is fine in the bigger picture of Nature reclaiming a sick and weakened plant but you might not feel fine if it’s one of your favorite plants dying. There are anti-fungal pesticides out there. I’m not recommending them, quite the opposite. But, if it’s a really valuable plant, I would be remiss to not mention they do exist.
For my own plan of action, and what I do recommend, is to concentrate on creating healthy plants and soil conditions. If some plants do succumb to a disease, even with good growing conditions, then perhaps they are not the right plants for my garden. Our goal is resilience and there are plenty of other plants that can thrive in our setting, even with climatic challenges. Plants that need undue attention do not fit our goal for resilience.
In summary, one of the keys to healthy soils is good microbial activity. Fungal soils have a symbiotic relationship with woody plants which creates a system of better health for both organisms. We should follow this example. We should do what we can to encourage soil health and it’s just as important to avoid actions that harm it. What we give to the ecosystem will be returned in kind.
— By James Young
James Young is the owner of Blue Wheelbarrow Landscaping in Edmonds.