Repotting and getting rid of old soil

[Bobbe]

Hi,

Been into bonsai for some years now and never got any clear instructions or ideas related to removing all the old soil from a Juniper or other conifer.
The ones Ive repotted (from nursery containers or the garden) Ive left 40-50% of the old soil and roots closest to the tree. The new soil is a free draining mix of your typical ingredients, the trees are doing great.

Ive always figured Id eventually get all the old clay like soil away with future repottings to avoid root rot and other issues.

So in a few years when I start repotting these trees again, how can I remove the "inside" soil closest to the tree and still leave some of the "old" soil? Seeing as the new soil mix is quite coarse and the old is solid, Im afraid trying to remove the old dirt will end up in a bare rooted tree. I can easily scrape the top layer off, but getting into the main root ball seems like its not going to happen.

Is this an issue or will the nebari eventually "push" out the bad dirt.

Tried the search functions here and on google but didnt find anything but the usual "do not bare root", "leave X%" and so on..
Thanks for any input

 

[TomB]

search on here for 'half bare root' technique, that's a way to accomplish what you are talking about. The 'bad dirt' will always be there unless you remove it.

 

[Bobbe]

Thanks Tom,

Seems like just the ticket.

Here is a short explanation (by Bonsaichile) for quick reference "HBR=Half Bare-root. It is a technique to gradually replace the native soil in pines without stripping them fully of mycorrhizae. Essentially, you bare root one half of the root ball one year and the other half one or two years later. "

 

[plant_dr]

There is a difference between repotting Junipers and pines. Pines need the half-bare-rooting technique to preserve the mycorrizae fungus that forms a symbiotic relationship with the pine roots. Junipers and do not depend on the mycorrizae partnership and I'm pretty sure most other conifers do not either. Fo s a juniper

 

[Bobbe]

Ive heard this before, but at the same time also hear most people recommend to leave anything between 30-60% of the rootball and generally seems too risky to bare root. This of course is dependent on the condition of the tree and other procedures that are done at the same time.
Personally, Im happy to take it slow and remove the original soil within 3 repottings and say 3-10yrs. My climate is not too wet and I can protect the tree from too much moisture should I have a rainy fall. Mainly concerned about overwintering and excess moisture collecting around the tree in the old soil.

 

[cheap_walmart_art]

I've also read on here taking old soil out in slices like a pie. Its a question I have as well - I have several junipers in need of repotting but the root ball around the trunk is damn near solid. I repotted a couple of them just cleaning out the perimeter roots and then repotting that in better substrate, and they're doing ok this season, but I know that won't solve the problem of a solid inner root ball with dusty old soil and I will need to address it at some point.

 

[bonsaichile]

if you dont want to risk it, just hbr them. In any case, I believe the advice is not to take more than 30% of the roots. You can take soil away without cutting any roots. 2 different things.

 

[leatherback]

I find that healthy junipers don't mind too much when you gently remove the old soil. Just don't ami for clean roots, but remove lumps when repotting. After 2 or 3 repots you have all removed.

 

[Bobbe]

Thanks for the input everyone.

I suppose you have to return to HBR every 5-15yrs when your soil mix/fert/moss starts to clog up the center again.. Or would you keep on top of this with every repot after you have initially made the transition to all bonsai soil? Basically HBR every time you repot?

The rootball gets tighter as it grows, probably containing some dead roots and other organic decomposing material. Seems like it would be impossible to keep only good soil if you would not constantly keep up on it.

Either way, Ill keep the HBR process in mind for future repotting sessions.

 

[M. Frary]

I've also read on here taking old soil out in slices like a pie

You've misunderstood the slice like a pie term. It's a thing we use on nursery pines that are root bound.
We saw half off of the bottom of the rootball. Roots and all. Then you make verticle cuts from the outside of the rootball toward the trunk. Those are the slices. You aren't removing a thing. You are just cutting roots.
I suppose you could do this to just about every nursery grown tree but I only use it on pines.
Junipers......I bare root them completely with a hose,untangle them and cut them.