Two years ago, we moved to a new garden, it was winter and with the regular and sometimes torrential rain, the soil was sticky and boggy. The whole vegetable garden area needed reconfiguring as much of the runoff from the house paddock flowed straight into it and had no way to flow out again. The rest of the property was scattered with lovely large trees, many of which needed pruning to open up the pasture for better grazing, and there were a few hectares of pine trees. Having used our own homegrown tree mulch in the past we knew what a valuable resource all these trees were.
Work began with reshaping the vegetable gardens, using swales to guide the water flow around the gardens and away from the beds. The paths between the beds were dug out and the soil spread over the beds to raise them, these paths were then filled with woodchip, mulched from tree pruning’s to a depth of 100 to 200mm. All the larger perennial, shrub and fruit tree gardens also received a generous covering. Mulch is usually used to retain moisture during dryer months, but also as in our case, to allow excessive moisture to run away from mounded garden beds in high rainfall times. It reduces the amount of weeds and any that do grow are easier to remove, this is thought to be due to succession (more on that later).
As we use mostly ramial mulch it also provides nutrients and helps change the characteristics of the soil to a less weed friendly environment. Ramial mulch is made from the fresh cut branches, up to 7cm in diameter and mulched while the cambium layer is still green. Often leaf matter or tree buds are included in the mulch adding even more nutrient for the soil. It is considered to have the optimal balance of carbon to nitrogen when used fresh, becoming higher in carbon as it ages. An issue with using aged wood chip is it can result in a ‘nitrogen deficit’ where the woodchip and soil meets, this can be negated by adding nitrogen to the soil in the form of blood and bone or aged manure at the time of applying the mulch or just by using ramial mulch.
But wood mulch in and around your garden has another beneficial use, it creates a fungal-dominated soil. We saw this firsthand as our garden settled and found its rhythm, the wood mulch began to sprout. We had been experimenting with Korean Natural Farming methods (KNF), collecting indigenous microorganisms from old tree locations surrounding us. These were grown on to create fungal brews and added to the composts. We had spread fungi all over the garden and as any mushroom hunter knows the fungi bug is addictive. While we searched the wider landscape for fungi, beneath our feet our fungal networks were expanding.
Most people just think of fungi as the fruiting bodies (mushrooms) which we see above ground. But the main body of the fungi, called mycelium, is in fact below ground, spreading throughout the soil as a network of fibre like growth, called hyphae. These networks are very effective at extracting nutrients and water from the soil and mulch and making it more available to the surrounding plants. The beneficial fungi are great little workers within the natural environment, creating healthy soil biology, offering direct protection for the plants by producing anti pathogens and out-competing disease organisms.
There are two main types of beneficial fungi; Mycorrhizal and Saprophytic. Mycorrhizal fungi are the ones which form relationships with plants by either attaching themselves to the plant’s roots (Ectomycorrhiza) or by penetrating the roots cell structure (Endomycorrhiza). Their relationship is mutually beneficial, the fungi network, or mycelium, spreads its strands into the surrounding soil and extracts the nutrients, minerals and water from a larger area which it then releases to the plant. The plant in turn gathers carbohydrates, energy and fatty acids through its photosynthesis process and feeds these back to the fungi. This symbiotic relationship connects the fungi to other surrounding plants as well, creating a (chemical) communication network which can cover large areas. In fact, the largest known living organism in the world is the mycelia of the parasitic Honey Fungus in the Blue Mountains of Oregon, USA, it covers an area of over nine sq. km.
Mycorrhizal fungi will often produce fruiting bodies near the roots of their chosen plant companion, as the underground mycelium can be very fine this may be the only way you will know they are there without the use of a microscope. However, the mycorrhizal fungi which fruit above ground are generally associated with trees (ectomycorrhizae). The Fly Agaric, Amanita muscaria, (the classic fairy tale toadstool) is a well recognised ectomycorrhizal fungi which is often found in pine plantations, but it also forms relationships with other trees such as oak, spruce, fir, birch, and cedar. Another well-known and edible species is the Birch Bolete, Leccinum scabrum, which is found under birch trees. But within the vegetable garden you are more likely to have Arbuscular Mycorrhizal (AM) fungi which is in the Endomycorrhiza group, these do not produce above ground mushrooms and do their work invisibly. Studied through a microscope, soil scientists are still learning about their amazing possibilities. AM are the most common symbiotic fungi/plant relationship, and it is thought that 80% of all land plant families have an AM relationship.
The majority of mushrooms we see in our gardens are Saprophytic, the decomposers, and they are the most common type of all fungi, this group includes the common field mushroom Agaricus campestris. Living on dead organic matter, they break down materials like chitin, cellulose and lignin, which are difficult for plants to digest. Their action of breaking down woody matter, leaf matter, manure, dead insects and bugs, creates humus and mineralised nutrients which can be utilised by plants. The soft bodied delicate fungi are usually the first to show up in your mulched areas, species like the common inkcaps, Coprinellus sp. They will digest the more readily available nutrients making them more bio available to the plants. In our garden we have experienced flush after flush of these short-lived mushrooms, the delicate heads pushing up through the mulch, opening like flowers and then dissolving into the black goo which gives them their name. Another tiny relation the fairy inkcap, (coprinellus disseminatus) form little clusters along the edges of the garden beds causing us to step around to avoid damaging their fragile beauty. Then as the mulch ages, larger, chunkier mushrooms begin to appear which are capable of accessing and digesting the nutrients within the cellular structure of the wood as they have a more vigorous mycelium and powerful enzyme excretions. These species often include the very common and brick red Leratiomyces ceres, also known a Chip Cherries (a rather fitting name). Bright and cheerful as they look spreading out over the mulch, don’t let the name fool you they are not considered edible.
Another interesting fungi which is common on woodchip mulch is Cyathus striatus, Fluted Bird’s Nest or Splash Cups, thus named due to their little nest like cups with a few peridioles (capsules of spores) in each which look like little eggs. These curious little fungi are so camouflaged by their colours and size they are easy to miss unless you are weeding or fungi hunting. It is the mycelium of these Saprophytic fungi that is most obvious under your mulch or in your composts, forming quite thick white clusters of hyphae. Pull the mulch back, move a board or brick and we see clumps of hyphae, a vivid white against the dark browns of decomposing wood, as the mycelium spreads throughout our garden.
The last group of fungi is the second largest and yet probably the most studied from a garden or horticultural perspective, Pathogens. These can be present as rust, root rot, brown rot, blasts and smuts etc. While many resources are directed towards the fighting of these fungi, the fact is that fungi are the cleanup crew. If they are attacking your plants something must be out of balance, if we work on strengthening our soil and therefore plant health, our plants will have better resistance to fungal pathogens.
It is this cleanup function of fungi which has made them a useful tool in the battle against man-made pollutants. Myco-remediation is the term used for the process of using fungi to transform environmental toxins such as heavy metals, petroleum, herbicides, pesticides, pharmaceuticals and many more. Their digestive enzymes can degrade these substances into generally harmless compounds, though in some cases these compounds can accumulate in the fungi. The shaggy ink cap (Coprinus comatus) is a common edible mushroom which can remove mercury from the ground but as it accumulates the mercury in its body, it can become toxic. So, it would pay not to eat fungi from known contaminated sites. The good news is even plastic can apparently be broken down by something as simple as the common oyster mushroom.
But there is another great side to these amazing fungi, the edible one. There are a number of popular edible mushrooms which are able to be introduced to your garden, most are grown on logs such as Oyster, Shiitake and Tawaka. But the most impressive of these edible garden fungi and which can be grown in your wood mulch, is the King Stropharia or Wine Cap (Stropharia rugosa-annulata) capable of growing to an amazing 30cm in height and diameter. It also is a very strong decomposer with a dense mycelial mat, breaking down the wood mulch into nutrients for your plants and into beautiful soil, plus it is apparently capable of gray water filtration. Spawn for the King Stropharia can be brought online and is mixed into a bed of thick wood mulch in your garden. With adequate moisture and mulch, it should begin fruiting within couple of months to a years’ time and continue to provide you with plenty of mushrooms for many years.
Often in our ‘conventional’ gardening and farming practices the beneficial fungi and other microbial life struggles. The use of frequent soil tilling, fungicides, pesticides, herbicides and frequent fertiliser application (especially soluble salt fertilisers) and even overgrazing, destroys the fragile fungal networks and their relationships with plants. Walk through old bush lands and you will see just how diverse and amazing these fungal networks can be. But these forests are highly fungal, which is not what we want in our food gardens and orchards, this is where the word succession comes in.
Succession is where one ecosystem is replaced by another as the soil and environmental conditions change and plants respond to these changes. Soil scientists studying the microbial world say bare rocky soil is at the highly bacterial end of the ecological succession, it moves on to scrambling annuals then to deeper rooted annuals and annual grass species, the fungi increasing slowly through each stage. The perennial herbaceous plants and grasses are just before the 1:1 B:F ratio (Beneficial Bacteria to Beneficial Fungi ratio) where vegetables usually thrive. The succession moves on to woody perennials, shrubs and vines between approximatly 1:2 to 1:5 B:F, with orchards said to do best at about 1:10. Deciduous trees range from 1:5 to 1:100 B:F with the evergreen and old growth forests being very highly fungal at 1:100 to 1:1000 B:F. By looking at what is currently thriving in your garden you can work out roughly where your ratio is at and changes you might need to make. But we also need to limit the practices that do harm and increase our use of mulches, diverse plantings and take the steps needed to start bringing our land back into balance. There is a whole new world to explore beneath our feet and bringing back the fungi is just a starting point into the soil health journey.
For more information, please check out:
And Korean Natural Farming at https://naturalfarminghawaii.net/