Mycorrhizae

**Brett S** · Posted: Fri Mar 07, 2008 3:26 am Post subject:

Ok optimum growing conditions for a tree will always be in the open ground. I think we can put that in the settled box.
It seems that the conditions experienced by trees in a pot(stressed) can be improved upon by using a different soil medium than they experience in the open ground.
In effect we are trying to get the most efficient soil medium so the tree can be less stressed in the confines of a pot.
In the confines of this pot we must supply water, air, and nutrients. To simplify this discussion I will include trace elements and any other element that the tree uses in the nutrient heading?

To do this we aim for a medium with water retenion that sits between 70-25%(looked for the text that staed this but came up blank?) for a fair amount of predictable time.
This gives us the best chance to keep the tree in optimum fresh miosture and air levels in a pot.
There has been a move towards inorganic soil that meets the water retention requirments but requires the continual use of fertilisers to maintain optimum nutrient levels available.

In my learning I have been instructed that a large amount of mycorrhizae shows a great growing medium
such as this thread from the IBC
http://internetbonsaiclub.org/index.php?option=com_smf&Itemid=133&topic=5966.0
It seems obvious that these trees in this thread are growing well.
So were do these observations leave us?
If Colin is correct in stating staing "Indeed, as we will see later, mycorrhizal fungi would probably not survive for long in such conditions[moist yet well-drained soil with a good supply of readily available nutrients ]anyway"

Then it seems we must look at a high amount of mycorrhizae in our soil not as a good thing but as an idication that we can make improvements to the medium.

Chris states

**Brett S** · Posted: Fri Mar 07, 2008 3:51 am Post subject:

Or should we be saying that with the trees adaptability to infertile soil by way of mycorrhizae we are able to produce a growing medium that has great water retention/drainage.
Maybe the high amounts of mycorrhizae is an idication that we have givin the optimum conditions for the tree to deal with low nutrient levels.

**Tachigi** · Posted: Fri Mar 07, 2008 12:24 pm Post subject:

I think the point is being missed. Mycorrhizae main function in regards to the host is that of a harvester. It converts nutrients and water into a forum that maybe taken up by the tree more readily. This regardless whether it be organic or inorganic soil. That is its sole function, not to make the soil more feritile.

The statement that "high amounts of mycorrhizae is an indication that the soil needs to be improved" is not really valid. Since if there is a high amount then the tree is getting all the nutrients it needs. This high level of mycorrhizae in bonsai culture can be viewed as a bad thing depending on the stage of development.

Colin once related a story when we were having an in depth conversation on this subject. While working at the Arnold arboretum he was repotting a Hinoki (if memory serves). At repotting he found that the roots were encased in mycorrhizae so thickly that it literally looked like styrofoam and could be broken away as you would styrofoam. What he noticed from this condition is that the roots had not grown significantly since its last repot. The mycorrhizae had colonized the root system so heavily that the tree felt no need to extend its feeder roots in the search for nutrients as the heavy colonization was providing the tree with all it needed, thus retarding the development of the nebari.
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**Brett S** · Posted: Fri Mar 07, 2008 5:13 pm Post subject:

**Chris Johnston** · Posted: Mon Mar 10, 2008 12:10 pm Post subject:

I don't think that one can make the distinction that high amounts of mycorrhizae indicates the soil could be better. Since we can all agree on the science of the mechanism involved, let's look at other conditions that lead to heavy mycorrhizae colonization, as well. Not so much research there, but one could argue that there are plenty of nutrients readily available in soilless mix when one uses organic fert. cakes to feed, and does so effectively. It's an area of mycology that probably won't get a lot of scholarly research, so supposition may have to suffice for now.

So the mycorrhizae colonize the pot and enable roots to take advantage of nutrients in parts of the soil the roots have not reached yet, and in return they get to use the carbohydrates produced by photosynthesis as all or part of their own nutrient requirements.

Colin's article on mycorrhizae is thoughtful and thought-provoking, but I was reading the version from his book, "The Art of Bonsai Design." That one is slightly more extensive, and, I think, complete than the version presented here, and leaves a little less guesswork.

Great discussion!

**Brett S** · Posted: Tue Mar 11, 2008 5:05 am Post subject:

**Chris Johnston** · Posted: Tue Mar 11, 2008 8:50 am Post subject:

Perhaps Colin could be persuaded to amplify his statement that you quoted. This was not the impression I got from reading his article in print at all. I'm also not certain that he wrote it as a certainty or that it was a certainty in the literature, it seems to be a more possible relationship in the wild, and it may or may not translate into pot culture.

But yes, the mycorrhizae do extend the root's reach to every particle of soil, whether the root can reach it or not.

HoYoku · Joined: 11 Mar 2008 Posts: 3

Taylor Brown · Joined: 09 Feb 2008 Posts: 15

WoooHooo Hi Mr Colin Smile

I'm so glad you answered. The mycorrhizae is a fungus like a mushroom. So does that mean there are 15 different mushrooms they collect the spores from. Do all the the spores help all trees or are some better than others for different trees. Sorry for all the questions I have a science fair coming up at school and was thinking maybe this might be cool to do as a project. Then I could be known as the fungus queen Laughing

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irene_b · Joined: 08 Feb 2008 Posts: 92 Location: Texas