Japanese black pine - Mycorrhizae growth in roots

[pinewood]

Question for the more experienced JBP enthusiast.

When using akadama, scoria/volcanic rock, pumice and or diamotite as a growing medium, there seems to be no Mycorrhizae growth in the roots at all. This is also true in the established trees in japan ( as seen online when they report)

However, using a soil mix with a high volume of pine barks with coarse river sand seems to make Mycorrhizae thrive in the roots. Mycorrhizae obviously plays a important function in plant health. Are we inadvertently forgoing this important aspect of root health by using the substrates listed above?

[treeman]

Question for the more experienced JBP enthusiast.

When using akadama, scoria/volcanic rock, pumice and or diamotite as a growing medium, there seems to be no Mycorrhizae growth in the roots at all. This is also true in the established trees in japan ( as seen online when they report)

It's there even though you may not see it. Often depends on the time of year.

[pinewood]

It doesn’t seem to be as evident as a pine bark/sand mix.

Reason why I ask is a gentlemen I know only plants his JBPs in bark/sand and advocates never reporting or disturbing the roots unless moving to a smaller etc. some of his pines have been in the same bonsai pot fir 20-30 years without repotting which goes against the general convention of repotting bonsai every 5-8 years. Yet his pines look very healthy. The surface soil in his pots are as hard as a rock, some are that pot bound that they have even pushed above the pot line.

He believes in minimising repotting and disturbing the roots as this is one of the biggest impediments to good JBP development.

[Gerard]

I agree that most people in Australia re pot their pines too often and we should consider the age of the tree. Older trees with a well established root structure will need potting less often. (Probably once every 5 or six years.) younger trees more often. The major consideration should be percolation, the roots need water and air. Once the soil particles break down and water lacks penetration into the soil we would expect the tree health to deteriorate. A tree which has not been re potted for many years will need less work because it will have less vigour.

[TimS]

I have one of my shohin size JBP in akadama, the mycorrhizal activity is rampant. I repotted it last year which looked like maybe 5 years since the one before going by how thick the mat of roots was. I won't repot it again anytime soon.

[wrcmad]

Question for the more experienced JBP enthusiast.

When using akadama, scoria/volcanic rock, pumice and or diamotite as a growing medium, there seems to be no Mycorrhizae growth in the roots at all. This is also true in the established trees in japan ( as seen online when they report)

I disagree.
I use both akadama/pumice/diatomite and akadama/pumice/scoria mix for my JBP's. Some of them have so much mychorrhizae activity that even the soil surface is coated in it, and it starts to travel up the nebari. When I lift them from the pot, it is often one white solid mass.