There is no doubt that mycorrhizae fungi play an important role in plant growth. They help aggregate the soil which in turn provides plant roots with better access to water and oxygen. Their symbiotic relationship with plants helps them access water and nutrients. It is only natural that companies want to sell these fungi to you. Don’t fall for it.
Mycorrhizae Fungi
Mycorrhizal fungi (mycorrhiza) are found in all soil where plants grow. They form large networks of fine filamentous growth throughout the soil. They associate with plant roots; some even burrow into the roots to create an even greater association with plants. About 80% of all plant species form some type of association with these fungi.
Think of mycorrhizal fungi as a vast network of very fine plant roots. They are not plant roots, but they behave in similar ways to plant roots. They burrow into nooks and crannies in the soil and collect water and nutrients for the plants. In return the leaves of plants send sugars to the fungi as food. Given this important association it is natural for one to think that it would be beneficial to add more mycorrhizal fungi to the soil. For a more detailed description of mycorrhizal fungi see Microbe Science for Gardeners.
Arbuscular Mycorrhizal Fungi
There are two basic types: EM and AM.
EM fungi (ectomycorrhiza) form associations with only about 2% of plants, mostly the woody plants like trees and shrubs. Since woody plants make up a large portion of the plant community, they are important to natural ecosystems but they are not usually found in commercial products for the garden.
AM fungi, called arbuscular mycorrhizae (a type of endomycorrhiza), make up the largest group and form bonds with the majority of plants. They provide mostly phosphorus to the plant. These are obligate symbiotic fungi, which means they can not survive for long without a host, although they can produce spores (a types of seed) that can survive until a host root shows up. This is the type found in commercial products.
The fact that they can survive as spores is important because it makes it easier to produce them. Commercial products contain a combination of spores, small fragments of mycelium and small pieces of roots that contain bits of fungi. Together these are called arbuscular fungi propagules and the number is listed on some commercial packaging. For example one product claims to have “60,000 propagules per lb”.
Facts About Mycorrhizae
- Garden soil already contains vast quantities of mycorrhizae, or at least it does if any kind of plants grow in it. Adding more is a waste of money, since they are already in your soil.
- Manufactured mycorrhizae consists of 2 or 3 types of fungi. It turns out that there are hundreds if not thousands of different kinds in your soil and some of these are very specific to certain types of plants. How do you know your plants will benefit from the 2 or 3 types you buy?
- Manufactured mycorrhizae are heat sensitive. If the container is left in a greenhouse, or a transport truck too long, the heat kills the fungi. There is no way for you to know that the product you buy contains active fungi – they could all be dead.
- Manufactured mycorrhizae are of a specific species, almost certainly from an area that is foreign to your soil. It is possible that these foreign species inhibit the growth of your native species. You have no way of knowing but it is never a good idea to import foreign species of any kind into your garden.
There is just no good reason to buy mycorrhizal fungi for your garden.
Special cases
There are some special cases that might warrant the addition of mycorrhizal fungi.
Bare Soil:
Soil that has no plant growth probably has few natural fungi. It would seem that this would be a good case for adding them. The problem is that if the soil is not suitable for plant growth, it is probably not suitable for the growth of mycorrhizae. Adding them will simply result in them dying. If you want to grow plants in this soil you first need to solve the problem in the soil. As plants start to grow, native mycorrhizal fungi will also show up, naturally.
Sterile potting soil:
Sterile potting soil used in containers has no natural fungi. Studies have shown that adding mycorrhizal fungi to this type of environment can have some positive results. Keep in mind that the main value of the fungi is to provide the plants with water and nutrients. In a potted situation, many gardeners over water and over fertilize, negating the benefit of the fungi. If you water and feed your plants regularly, there is little benefit to adding mycorrhizal fungi.
Commercial Inoculants vs Compost
Most commercial products have a dozen or fewer species in the product. Some don’t even list the species. A recent analysis of a compost sample showed that it contains 305 fungal species and 360 bacterial specials.
In a recent review I checked with 5 commercial product manufacturer and asked them for proof that their product worked. You can read about the results in Mycorrhizal Inoculant Investigation – Do They Work?.
The Latest Science About These Fungi
The latest news investigates how tilling affects fungi in soil, and how effective commercial products have been in agriculture. Read all about it in Mycorrhizal Fungi – The Latest Scientific News.
The latest data clearly shows that claims such as “In soil that has recently been tilled/worked, mycorrhizae will be lacking” are not true.
Better Ways to Build Soil Health.
10 Easy Soil Testing Methods For Measuring Soil Health
Preventing a Nitrogen Deficiency in Soil – How to Manage Nitrogen Levels
Soil Bacteria – The Myth of Identification & Management
10 Fertilizer Myths That Will Save You Money
I think there is an element missing from this conversation and it would be what method of farming are you using? Are you leaving the soil as permaculture or “no dig”, are you hydro or aquaponics?. Is this a new garden bed or an established one?. If you have an established garden where mycorhiza have plenty for association and food, it would be the same as any wooded area and would be much more beneficial to feed them rather than incorporate more. This is the reason wood chips, sawdust or leaf mulches can have such amazing result, most of which farmers are ignorant, most think it is just water retention. In the case of typical farming where tilling is used, or if there are no plants in the soil prior to planting, then you have essentially a desert. Most of the ecology of the soil will die, the plants do ok in the short run as they are able to absorb from the dead bacteria and fungi, but it is a slow cycle of death. In this case innoculants would help, but you would still be better off if you have some wooded area, to bring some of the leaf litter onto that soil and cover immediately with a wood mulch. If this is a garden bed for vegetables, mycorhiza should be incorporated with the seeding soil mix, as you want the plant to have the quickest growth possible.
The main issue in agriculture today is that we grow to destroy ecosystems not to create and regenerate. Otherwise we would not have monocrops, we would have complete interplanting from veggies to bushes to trees and vines. When everything is planted to create a perfect ecosystem for a forest of plants, indeed innoculant would be redundant. Unfortunately we live in no such world.
It is true that tilling reduces fungal populations, and maybe even microbial populations. But the key question is, will adding additional fungal products make a difference in such a situation?
Hi Robert.
Your site is good but does tend to reflect a reductionist science training.
It tends reflect a lack understanding of soil ecology which requires a systems science approach, which many good natural gardeners/farmers have the ability to intuit broad patterns and connect the dots that reductionist science provides.
You need to do a lot more reading about soil ecology. There is no way that overwatering and over fertilising is a practice to condone, this is killing the planet for humans ref Gulf of Mexico dead zone. Even in fertile soils mycorrhiza and companions are necessary for optimum plant and human nutrition (trace elements biochemicals), they are the main factor in building soil carbon and natural structure.
“Even in fertile soils mycorrhiza and companions are necessary for optimum plant and human nutrition ” ??? I never said it was not important.
Hi Robert,
I have to agree with Duncan in that your science and your knowledge-base is not sufficient to be writing on this topic.
It is important to distinguish between scientific academic rigour and the whims of an “experienced gardener”.
Arbuscular Mycorrhizal fungal species are now known to associate with over 90% of terrestrial plant species. The plants form associations with multiple fungal species at the same time and the benefits range from mineral and nutrient acquisition (particularly phosphorus), to water collection, to disease prevention, to drought tolerance, to inter-connectedness between plants of the same and different species. Your statements seems to reflect simple intuitions that appear logical but are only scratching the surface of this vast and complex topic. You are over-simplifing to the point of being irrelevant.
For you and your readers, please consult some material published by actual experts in the field of mycorrhizae: Larry Peterson, Hugues Massicote, Paoloa Bonfante, Mark Brundrett, David Read, Sally Smith, Maria Harrison just to name a few. Also, I highly recommend that you and your readers have a look at “Mycorrhizas: Anatomy and Cell Biology” published by NRC press and authored by R. Larry Peterson, Hugues Massicotte, and Lewis Melville (2004). Also, “Mycorrhizal Symbiosis” published by Academic Press, London and authored by Sally Smith and David Read (1997)
1) I am not reporting on my experiences. If you read any of my material, including this post, you will realize that I report on what scientists say.
2) In your long comment you failed to provide any evidence that purchasing inoculant products for the garden is worthwhile. If you have such evidence, present it so it can be discussed. Nor have you pointed out any fact in the article that you consider to be incorrect – I guess you agree with my statements.
1) You provide only two references. One is a broken link to a publication by Dr. Chalker-Scott, who appears to have published once on mycorrhizae in a non-peer reviewed periodical. The other is a photo credit. Where are your references for the claims that you make?
2) There is a consilience of evidence that mycorrhizae add to the biodiversity of the soil and improve soil ecology. There are also countless examples of greenhouse grown and field grown plants that show the benefits of mycorrrhizae. Why would a garden be any different? There is also a consilience of evidence that shows that the different species used in commercial production associate with a wide variety of plant species and these species such as Glomus intraradices, for example, are cosmopolitan found all over the world and in association with many different plant species. Synthetic fertilizers, herbicides, pesticides, grass seed are all heat sensitive and they are shipped world-wide with good efficacy. In addition tot he two previous references that are very comprehensive on the subject of arbuscular mycorrhizae, I also offer the following: “A Review: Beneficial Effects of the Mycorrhizal Fungi for Plant Growth” (2001) by Mohammadi et al. Published in the Journal of Applied Environmental and Biological Sciences. Also, “Arbuscular Mycorrhizas: Physiology and Function editied by Y. Kapulnik and D.D. Douds Jr. (2000) and published by Kluwer Academic Publishing. These are real scientific publications with peer-review, not opinion pieces written by non-experts.
You are very good at asking others for references but lack the rigour to provide your own. Please stop spreading misinformation.
I think you missed the point of what I said. I agree mycorrhizal fungi are import to plants. What I disagree with is that adding them to your garden will make any difference. They already exist in your soil, or if they don’t the soil environment is not conducive to their survival, so adding more won’t make any difference.
Robert, I will attempt a more direct question.
What facts/information are you using to base your claim upon?
What is it about a garden environment that is so different from the rest of the outdoors, labs, etc. that there would be no benefit to adding mycorrhizae? You don’t know what species are in your existing soil unless you have surveyed the roots microscopically so how do you know a potentially new species to your garden or an additional amount would not make any difference?
How is the soil environment of a garden not conducive to mycorrhizal fungal survival?
You have made authoritative statements with neither scientific references nor sound arguments to back them up. That is the problem here.
Are you aware that mycorrhizal mycelia can create vast networks that encompass miles of underground area. The mycorrhizae in your garden could be gathering nutrients and water from miles away.
You must provide references or an argument, otherwise, this is just your opinion and it is not presented clearly as an opinion only.
I have looked for scientific evidence that adding fungi to soil results in a change in populations in a real world environment. I have not been able to find such evidence.
If you have such evidence, I would be happy to look at it. But it needs to include controls, showing the change in fungi populations in the garden. That is step one. Step two then is show that the change results in a benefit to the plants.
I have discussed this topic with 3 researchers working with mycorrhizal fungi and they all agree that it is unlikely that there is any benefit to adding them to a garden environment.
I think I am beginning to understand your logic now. You have not found any evidence, therefore, none exits. Is that accurate?
Please define “real world environment”. It is doubtful that any academic papers have been published on the effects of mycorrhizal fungi specifically in gardens if that is what you are looking for. I would imagine that the main reason for this is that it is much easier to secure funding for agricultural or restoration research. Also, I am not aware of any academic research labs that do gardening studies.
That being said, the scientific literature is flush with support for the influence of mycorrhizae on soil ecology and plant benefits. There is no reason to expect a garden to be different.
You have been asked to provide references but you have not provided any despite claiming that you have discussed with 3 different mycorrhizal researchers. How about providing their names at least?
Without evidence there is no proof.
It does not have to be in gardens – can be farms.
The science shows the benefit of fungi once in the soil. It does not show the benefit of adding more to the soil.
Hi Robert, this is a very interesting topic you’ve raised and I appreciate the thoughtful comments that have been added to the discussion.
The trouble with the “science” of research is that they need a controlled environment where only a few variables can be measured/adjusted. Gardens are so vastly different that these “scientific studies” are generally pretty off-target unless you can exactly replicate their environment in your garden – even then, an unmeasured/unmentioned variable could give you vastly different results.
This also applies to anecdotal evidence as the person giving that could be in a totally different environment to you. Or cynically, they might be pushing an agenda for whatever reason.
So where does it leave us keen amateur gardeners? Each of us have to do our own research! Okay, listen to “old-timers” in our area with their anecdotes (but add a pinch of scepticism). By all means read the research to give you ideas to try. In the same way watch Youtube to suggest a possible idea. But in the end, go into your garden and do these trials yourself. And use the ones that work for you. Happy gardening!
It is not difficult for research to establish controls. It is true, that when such a test is done in only one location, it can be difficult to extrapolate the results. Does something that works in Florida work in the north, for example.
It is also true that a lot of stuff has not been tested.
In the absence of science we need to rely on experience – ours and others. What is critical here is to evaluate the quality of the advice – how much do you trust it? Unfortunately, much of the internet can’t be trusted.
Interesting information. I have my doubts about the need to purchase fungi products. I have a plot of forest that I use for my own garden research, especially for improving water retention during droughts. So far the best products I have used for plant health and water conservation is wood chips and leaf litter which mimics what naturally occurs on a forest floor. These break down within a year, sometimes less, and provide nice rich soil. The herbaceous layer of the forest has improved and so have the plants. I don’t use commercial fertilizers either but I do own horses and use the composted manure as an additive in the flower beds. My soil is primarily clay except for the upper horizon. Most plants seem to do well in the clay but there are challenges.
HIRobert
You asked for referance about any benifits on adding fungi or bactiera to the soil, have you never workrd with compost teas, i spent last summer running a trial to degrade thatch on golf greens .We worked with white rot fungie theses are the good guys braking down the matter in the woodlands. the results we amazing. Reduced thatch by 60 to 70% improved rooting less diseses.cleaned up 95% of the black layer
Infact they use the Phanerochaete Fungi all over the world to clean up soils you should take a look its amazing how they are saving 10,000s of soil going into land fill by just adding them to contaminated soils.
Best Rgards
Andy
But no references??
Having kept fish most of my life, I can attest that, in the case of bacteria, you MUST inoculate.
Im not sure why it would be so different with fungi. There are times when a population dips to the point of disaster and adding to the population will change the balance just enough to cause that population to become viable.
After the initial inoculation, one rarely needs to inoculate again, in the case of bacteria, and likely for fungi as well. But, in rare cases, I have had to reintroduce bacteria to an existing population because, for some reason, the bacteria had dropped to dangerously low levels. Once added, the boost in numbers effects the balances in the water in a way that helps further bacteria to repopulate on their own.
Why should it be different for fungi?
Not sure what fish as to do with it – but you don’t have to inoculate. There are millions of bacteria in each gram of soil, and scientists don’t even know what 80% of them are. How can any gardener know which need to be added?
Show me one reference that shows a benefit from adding either bacteria or fungi to soil?
Just pee on the soil, add as many varieties of organic material, or even your dog’s poo. Nature will flourish. Innoculants is like taking expensive health supplement. They are costly and gives one a feel-good .for a short while. Culitvate Nature…it will reward you at little or no costs to your gardening
Biochar can be self-made and added to the soil. The micro-pores are ideal for microbes. It is not just the fungi but the microbes. Healthy soil is not a formula. It is about putting in the effort. Plus do not forget about having sufficient water.
Your readers may find this interesting.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717633/
In a sense it both defends and re-butts your position.
Humanity has done such a disservice to the balance of our soil. It makes sense to try to bring back what we’ve undone.
There is no harm in trying some of the products offered. Research is needed before running out and buying anything off the shelf.
I’m doing aquaponics so I find adding fungi is beneficial for increased nutrient uptake. Especially in a case such as tomatoes which need a little more phosphorous.
You can throw this in your search bar for additional sources.
https://scholar.google.com/scholar?as_ylo=2014&q=best+mycorrhizal+fungi&hl=en&as_sdt=0,22&as_vis=1
thanks for posting – interesting summary.
I planted trees in a former agricultural field (in which there had been tillage, use of chemical fertilizers, pesticides…).
I initially found the soil very compacted and muddy (full of water, without air).
Some of my trees have died, probably because of the lack of drainage.
I bought some mycorrhizal fungi inoculant (with 8 endo and 7 ecto), and put some of it in touch with what remained of the tree roots.
One year after, I found that the structure of the soil around the trees had dramatically improved, becoming more crumbly and aerated , and that some of the trees were doing better.
I can’t prove the improvement was the consequence of the fungi inoculation (at the same time, I have also mulched the trees with cardboard or jute mat), but it might well be.
I know I could have brought some soil from a nearby forest, but I didn’t have time for that.
I agree it may not be useful to inoculate an already healthy soil, but I believe it may help in a damaged soil.
It may also help when planting ecto plants (like oaks) in a soil which only has endo plants.
Even manufacturers of the product don’t make claims like this “One year after, I found that the structure of the soil around the trees had dramatically improved, becoming more crumbly and aerated “.
Is that your argument? Scientific studies seem to contradict some of the things you are claiming as “Myth”. There are some good point made, but IMO you go to far with your dismissive statements.
Do you have some references to support your claim?
Hi, Robort
My I konw how to buy your AMF inoculant ? And how many spores in the inoculant? wolud you please offer the accurate species name of the AMF?
What makes you think I sell this product? I am arguing that buying it is a waste of money.
Hi, mycologists here who specializes in ECM (ectomycorrhiza), but I know quite a bit about AM (arbuscular mycorrhiza). First, mycorrhiza is the short but correct way of writing mycorrhizal fungi. Mycorrhizae or mycorrhizas is the correct plural form of mycorrhiza, but writing “mycorrhizae fungi” is akin to writing “sports medicines.” It’s not common usage.
Let me address some of your points:
1. “Garden soil already contains vast quantities of mycorrhizae…Adding more is a waste of money, since they are already in your soil.” Not necessarily. It’s true that most soils already contain existing mycorrhizae, but not all mycorrhizae is created equal and some plants aren’t well colonized by mycorrhiza. Some fungi are more dominant than others, so adding a particularly aggressive species of AM could help your garden.
2. “Manufactured mycorrhizae consists of 2 or 3 types of fungi. It turns out that there are hundreds if not thousands of different kinds in your soil and some of these are very specific to certain types of plants. How do you know your plants will benefit from the 2 or 3 types you buy?” If you wanted to get technical, you could identify the fungi by looking through a basic stereo microscope. You could pinpoint the morphology of the fungi that are colonizing your plants by taking a root sample.
3. “Manufactured mycorrhizae are heat sensitive. If the container is left in a greenhouse, or a transport truck too long, the heat kills the fungi. There is no way for you to know that the product you buy contains active fungi – they could all be dead.” HIGHLY unlikely. Heat from a greenhouse or truck is unlikely to kill the spores of the fungus. You would literally have to autoclave the spores for some time before they would “die.” They aren’t nearly as heat sensitive as plants and can be kept viable for years and years. More of a concern is drying the spores. They become unviable if they are dehydrated, but that is unlikely to happen in a truck or greenhouse.
4. “Manufactured mycorrhizae are of a specific species, almost certainly from an area that is foreign to your soil. It is possible that these foreign species inhibit the growth of your native species. You have no way of knowing but it is never a good idea to import foreign species of any kind into your garden.” Yes, invasive non-native fungi is a concern for many mycologists, but most of the AM products in the market are EVERYWHERE. The introduction of non-native species only becomes a problem if you’re displacing more valuable fungi on a large scale. Lots of non-native species improve the growth of hosts. They will not likely inhibit growth, especially since AM uptake nutrients and water. Keep in mind, research is constantly being done and these commercial AM products are shown to be pretty mainstream and garden-friendly. Also, you could monitor the effects of the mycorrhiza by checking the growth of your plants.
So that’s my two cents. Hope you learned a little bit about mycorrhiza 🙂
Re: #1 “so adding a particularly aggressive species of AM could help your garden. “. There seem to be lots of lab studies and even agricultural studies, but do you have any references for studies in gardens?
#2 – true enough, but not something gardeners would do.
Thank you for your contribution.
#3 – You may be correct here. Quite a few places refer to the heating problem. A recent study looking at commercial products found that many of them were “non-active” – some dead, and some just not there.
if the heat from a greenhouse kills all mycorrhizae wouldn’t it all be dead in places with 110 degree summer days. all kinds of heat sensitive products get shipped all over the world
Yes, if the soil gets that hot – which it does not.