Mycorrhizal danger

Hopkinton, MA(Zone 5b)

Hi! I was talking to a compost tea brewer yesterday and he told me that mycorrhizea harms certain plants by stunting their growth. I'm fortunate to have heard this before I propagated seeds or transplanted this year.

I was informed about a web source with information about plants that don't respond to mycorrhizea such as cabbage, blueberry and sedge. Many Dave's Garden members are still waiting to plant so I wanted to help folks who are interested in finding out which type of mycorrhizea to use or if they should avoid it. The following page describes how mycorrhizea affect different groups of plants:


Thumbnail by NancyGroutsis
Northeast, WA(Zone 5a)

I will look at the thread, however just a quick question for you DoGooder. Are you saying there are more than one type of Mychorrizae? Think that is what you said. So, guess I had better read the thread. I did not know that. No idea. Jen

Hopkinton, MA(Zone 5b)

Jnette, I'm not an expert but as I understand it there are two major types of mycorrhizae: ectomycorrhizae and endomycorrhizae. 90% of plants benefit from the ecto type, 5% of plants benefit from the endo type, and 5% of plants don't need mycorrhizae. Also, some plants like willow benefit from both endo and ecto mycorrhizae.


Northeast, WA(Zone 5a)

Ok, time to do some research. Thanks, Jeanette

Ottawa, KS(Zone 5b)

Premier ProMix BX contains endomycorrhizae, and all of the different kinds of seedlings that I have started in it seem to benefit from it.

Apparently the fungus forms a symbiotic relation with the roots of the seedlings.

Fortunately for me I can purchase the product locally to avoid shipping costs. Premier ProMix BX is also available with a "biofungicide" that I haven't tried yet.

(not associated with any product or vendor mentioned or linked)

Central, TX(Zone 8b)

Beneficial microbes are all the rage this gardening season. I have a dry product that contains both ecto and endo M, and a liquid product, "Thrive", the version for vegetables, that I'm going to use. It's been highly promoted in our area. As for me...time will tell - I'm trying to give my veggies a "leg up" during this horrid drought we've been experiencing.

I attended a presentation last year about soil microbes and the effectiveness of beneficial types working in symbiotic relationship with a plants roots - extremely interesting. The advice was to add organic matter to your garden soil, provide enough moisture for them (your native population) to live and multiply to keep the cycle going vs. just pouring a "miracle product" on the soil thinking its going to make the difference.

See this Alpha-BioSystems link:

Happy Gardening,


Hopkinton, MA(Zone 5b)


I read the link that you provided. Looks like those products help the natural composting process in growing media. Regarding the drought issue you mentioned, perhaps adding greensand will help. Greensand has not harmed any of my plants and it has been especially beneficial to plants that need frequent watering such our umbrella tree and Million Kisses Begonia.


Everett, WA(Zone 8a)

Ecto is for woody plan ts like trees and shrubs.
Endo is good for, or needed by, almost everything else, e.g. flowers & vegetables.

I had heard some plants did not need them, but this is the first time I heard that mycorrhizae can hurt anything. Maybe it hurts some plants by giving other nearby plants a competitive advantage?

There are MANY kinds of endomycorrhizae, in fact, some plants' roots are symbiotic with up to four different species of "root fungi" at the same time, for maximum health.

I don't have an Internet reference for that, just a paper-and-ink microbiologyh text.

Here's one link to a long article:

Hopkinton, MA(Zone 5b)

RickCorey_WA, thanks for the link with mycorrhizae information! It says that mycorrhizae grow better in soil than in soil-less media, so maybe I will add soil and mycorrhizae to some of my seedlings to see if it helps their growth.


Northeast, WA(Zone 5a)

It's been a while since I read this and when I googled it I read that 5% were badly affected. Well, if that is all that it bothers, I'll take my chances.

Everett, WA(Zone 8a)

Hmmm, maybe that's one reason my seedlings get wimpy if I hold them in cells or pots too long. The roots really really DO need their symbionts.

I read one article about "multiplying" mycorrhizae for arid regions. You were supposed make a spore-rich innoculm by growing certain myco-friendly cover crops in healthy soil that started out with plenty of mycorrhizae.

"... a mixture of host plants are sown - members of the grass and legume family have been shown to be infected by mycorrhizal fungi easily:
maize and beans
or millet or other members of the grasses family with a legume such as lentil.
Onions or leeks are good too."

After 3 or so minths of growth, cut the plants down and stop all watering.

"This effectively kills the plant and tricks the mycorrhiza that has infected the roots into quickly releasing spores.
After one further week the roots of the host plants are pulled up, roughly chopped into 1cm long strips and mixed back into the soil. This soil and root mixture becomes your inoculum."

Northeast, WA(Zone 5a)

Rick you've been watching too many cooking shows.

I have been using it now for 3 years and have not lost any plants I can blame on it.

Everett, WA(Zone 8a)


I said:
>> this is the first time I heard that mycorrhizae can hurt anything
not that I knew anything myself about any risks.

My post immediatly above yours was suggesting ways to increase mycorrhizae in arid soils, and speculation that lack of mycorrhizae in my seedling cells might be making them wimpy if held too long away from real soil where they would find the mycorrhizae they lack.

I didn't mean to imply the opposite.

Hopkinton, MA(Zone 5b)

RickCorey_WA, that's interesting to know that some plants use more mycorrhizae than others. So, it's not just what's in the soil but the plant species also determines the level of mycorrhizae.


Everett, WA(Zone 8a)

The level AND the species.

I'll find that microbiology text tonight. It opened my eyes how many varieties there are, and how complex some plant species get. In some plant species, literally FOUR different species of mycorrhizae would take up residence in different parts of the root and soil, and each perform specialized tasks.

It must provide a major benefit, for such complex inter-species co-evolution to occur. I guess plants and fungi are smarter than politicians about co-operation!

Hopkinton, MA(Zone 5b)

RickCorey_WA, LOL! If only our politicians would work together as beneficially as plants and mycorrhizae.


Sierra Foothills, CA(Zone 8a)

DG ~ Amen!

Everett, WA(Zone 8a)

It gives a new meaning to "grass roots" organizing.

WShat's especiallyh cool to me is that both plant roots and root-fungi cooperate to both extract water and minerals from soil, but also improve soil's structure, drainage and water-retention. Win-win-win, in biological, mechanical and chemical domains.

Nature doesn't seem to have any problems about wsorking "accross the isle" and "out of the box", or "inter-disciplinary". I think Mother Nature forget to tgeach her children about "not my job" and "zero sum game".

Sorry I forgot to look for the microbiology text, but imagine that I typed 10 lines of dense Latin plus several "wows" and "cools". I recall that some would slip into viens in roots and/or root hairs, others would mostly sit on the surface of root hairs, and I THINK some actually penetrated root cells.

Both roots and fungi would change their morphology once they started living together.

Tomorrow, I hope!

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